The Metal Gear universe refers to the Smash Bros. series' collection of characters, stages, and properties that hail from the popular Metal Gear stealth-based video game franchise developed by third-party developer Konami. The long-running series is famous in the Smash Bros. community for being the first third-party game franchise to contribute characters and properties to the otherwise Nintendo-exclusive Smash Bros. series, mainly the series' main star, Solid Snake. The logo is the logo for FOX, the unit that Naked Snake hailed from in Metal Gear Solid 3: Snake Eater (also the logo of Kojima Productions, the developer of the franchise).
 Franchise description
In 1987, then-unknown video game planner Hideo Kojima, working at Konami, was asked to take over a project that had been intended as a wartime action game for the MSX2 home computer. Technical limitations to the MSX2 prevented Kojima from creating a game that had many bullets and enemies onscreen at any given moment, though, so Kojima made a decision to design and direct a game that drew inspiration from the film The Great Escape, wherein the focus of the game was to avoid visual contact and direct confrontation with patrolling enemies. His bosses' questioning over this decision nearly prompted Kojima to leave Konami, but after one of his bosses encouraged him to continue, he proceeded to complete and release Metal Gear on July 12, 1987. It is credited by many today as the progenitor of the stealth action genre in the video game industry.
Years later, Kojima was asked to develop an MSX2 sequel to Metal Gear, and the result, Metal Gear 2: Solid Snake, was released on July 20, 1990, introducing many of the evolved stealth gameplay aspects that would be present in the rest of the series. But it was only in 1998 when the September 20th release of the seminal third game in the series, Metal Gear Solid, brought the series into the mainstream. Universally glowing reviews and chart-topping sales propelled the Metal Gear intellectual property into a gigantic franchise, and it is often recognized as one of the key titles involved in popularizing the stealth action genre. In addition to featuring the gameplay style of the previous game in three dimensions, Metal Gear Solid made extensive use of cinematic cutscenes to tell a gritty, mature, twist-filled narrative like a film.
The Metal Gear franchise, often referred to with the name Metal Gear Solid due to almost every subsequent game featuring the word "Solid" in its title, proceeded to release a large number of sequels, prequels, interquels, expanded re-releases, and non-canonical side-games on a regular basis. In most of the games, the player takes control of an elite, artificially-enhanced special forces operative codenamed Snake - either it is Solid Snake in games set in the postmodern present, or it is his father, Big Boss, back when he operated as Naked Snake in games set after the Cold War era. A younger secondary protagonist codenamed Raiden is also sometimes featured in a leading role. The games have Snake, operating under the command of the highest orders of government, sneaking into the compounds of militant enemy forces that threaten Earth politically with revolutionary nuclear weapons technology, which in many cases take the form of a bipedal walking tank named "Metal Gear". Snake uses his stealthy cunning to bypass enemy guards that can be avoided, neutralizes guards and elite enemies that stand in his way with weapons procured on site, and interrogates hostages and enemies alike to gain directions and access to where he needs to go to complete his mission to neutralize the war weapons and the villains that threaten to use them.
Each release in the central Metal Gear chronology adds to the series' ambitious lore, which is closely grounded in the politics of real-world Earth from the Cold War onward. Core themes explored include many issues about nuclear deterrence, social engineering, artificial intelligence, information control, conspiracy theories, censorship, the manipulation of free will, and taboos such as incest and homosexuality. This takes place throughout narratives that are rife with betrayal, revelations of identity and family, and other plot twists that span many games. Depictions of Snake and other Metal Gear characters and elements in a more light-hearted air are usually relegated to non-canon side games and cameos, such as when Solid Snake became the first third-party character to be featured as a playable character in Nintendo's Super Smash Bros. series in 2006, in Super Smash Bros. Brawl.
What follows is the release history of the canonical Metal Gear continuity:
- Metal Gear (1987), on the MSX2, depicts the special forces operative Solid Snake, working for the U.S. special forces unit FOXHOUND in 1995, going on a solo infiltration mission into Outer Heaven, a compound in South Africa, to destroy the nuclear walking tank Metal Gear TX-55 being constructed by militant mercenaries. Snake discovers that his superior in the U.S., Big Boss, however, is secretly the enemy ringleader, plotting to make Outer Heaven the world's greatest superpower. Snake destroys Metal Gear and defeats Big Boss.
- Metal Gear 2: Solid Snake (1990), on the MSX2, has FOXHOUND's new commander, Roy Campbell, sending Solid Snake in 1999 on a mission into the Central Asian country of Zanzibarland, which plots to hold the world hostage by controlling the newly-discovered OILIX energy source as well as a stockpile of nuclear warheads. Snake discovers that Big Boss is the ringleader of this as well, and Snake ultimately kills Big Boss and destroys another Metal Gear being constructed named Metal Gear D, which was redesigned and improved from the last Metal Gear. Snake retires from FOXHOUND after the events of the game.
- Metal Gear Solid (1998), on the PlayStation, has FOXHOUND going renegade in February 2005 and threatening nuclear reprisal against the U.S. Government with another Metal Gear they acquired when they seized a nuclear weapons disposal facility on Shadow Moses Island, a remote island in Alaska. Led by the mercenary Liquid Snake, the terrorists' demands are the remains of Big Boss, whose genes can be used to mass-implant the traits of the legendary soldier into many soldiers. Roy Campbell forces Snake out of retirement to infiltrate Shadow Moses, kill all of the elite members of the FOXHOUND unit, and destroy Metal Gear REX.
- Metal Gear Solid 2: Sons of Liberty (2001), on the PlayStation 2, begins with Solid Snake, now operating for the non-governmental organization Philanthropy, infiltrating an oil tanker near New York in 2007 to investigate the development of the aquatic Metal Gear RAY, but one of Snake's enemies from the previous game, Revolver Ocelot now possessed by Liquid Snake to become "Liquid Ocelot", steals it and sinks the ship. Two years later in 2009, a reformed FOXHOUND sends a new operative, Raiden, on a mission into an offshore clean-up facility named Big Shell, wherein a terrorist group named the Sons of Liberty, backed up by the rogue anti-terror training unit Dead Cell, has kidnapped the U.S. president for monetary ransom and threatens to ignite the facility and Manhattan. Raiden's mission quickly reveals world-changing secrets about virtually everything around him.
- Metal Gear Solid 3: Snake Eater (2004), on the PlayStation 2, is the first prequel in the series, set in the Cold War in 1964, and stars Big Boss back when he was an elite operative of the CIA's FOX unit codenamed Naked Snake. An internal power struggle in the Soviet Union, instigated by the ruthless Colonel Volgin, threatens to prompt the Soviet Union and the United States to begin a nuclear World War III, and a spiritual precursor to modern Metal Gears, a rocket-propelled nuclear tank named the Shagohod, is part of his plans. The USSR asks the U.S. to assassinate Volgin before he takes over, so Naked Snake is sent to infiltrate the jungles of Tselinoyarsk in the USSR to battle Volgin, as well as his beloved mentor The Boss, who along with her elite Cobra Unit had previously defected from the U.S. to the Soviets.
- Metal Gear Solid: Portable Ops (2006), on the PlayStation Portable, has Naked Snake's former team, the FOX unit, breaking their allegiance with the CIA and going rogue six years after Snake Eater in 1970, and they target him as well. Naked Snake is captured and brought to Colombia, where he is interrogated for the location of part of the massive sum of money known as the Philosopher's Legacy. Naked Snake, with the help of a young Roy Campbell that had also been captured, must defeat the top members of the FOX unit and destroy an early Metal Gear model that is the backbone of their rebellion.
- Metal Gear Solid 4: Guns of the Patriots (2008), on the PlayStation 3, depicts Solid Snake in 2014, much older than he was five years before due to genetic issues that resulted in accelerated aging. The world economy now relies on continuous war fought between private military companies, and the soldiers' performance in combat is enhanced by nanomachines. Liquid Ocelot now plans to hijack the control network created through these nanomachines, so Solid Snake, with less than a year to live, is sent by Campbell on one last mission to tail Liquid across the world. Snake does battle with the all-female PTSD-afflicted Beauty and the Beast unit before taking part in a climactic final showdown that culminates the primary series' timeline.
- Metal Gear Solid: Peace Walker (2010), on the PlayStation Portable, is another interquel starring Naked Snake in his Big Boss persona, four years after Portable Ops in 1974. Now running his own mercenary group after having broken away from the CIA, Naked Snake is hired by the country of Costa Rica when a mysterious militant group, the Peace Sentinels, deploy themselves within its borders. Though they are merely the size of a land army, they threaten to endanger the balance of power between the East and West because Costa Rica does not have an armed forces of its own to do anything about them. The resolution of this incident solidifies Big Boss' perspective and decision to construct a nation entirely for his own group of mercenaries, which would become known as Outer Heaven.
- Metal Gear Rising: Revengeance (2013), on the PlayStation 3 and Xbox 360, is a spinoff that takes place four years after Guns of the Patriots in 2018. The different title reflects that it is not like the previous stealth-oriented installments in the series, instead featuring Raiden as a cyborg ninja taking part in a more up-front action game with a sword-based combat system. Raiden takes jobs for a variety of private military companies until he is forced to contend with other cyborg enemies from the self-proclaimed private military company Desperado Enterprises.
- To be released is Metal Gear Solid V: The Phantom Pain for PlayStation 4, Xbox One, and their predecessors, and is the first title in the series that is slated to have open-world gameplay structure. It is yet another interquel starring Big Boss, and is set after Peace Walker; in a prologue segment taking place one year later in 1975, Big Boss decides to infiltrate the maximum security prison facility Camp Omega in southern Cuba to, among other things, rescue an agent he previously fought, who carries an important link to the mysterious "Cipher" group. But Big Boss falls into a nine-year-long injury-induced coma at the same time his company is destroyed. After he awakens in 1984, Big Boss forms a new mercenary group, the Diamond Dogs, and assumes the codename "Punished Snake" as he ventures into Afghanistan - in the midst of the Soviet war taking place at the time - seeking revenge against those responsible. But an even more threatening plot by Cipher is soon unearthed...
 In Super Smash Bros. Melee
A popular story tells that during development of the Nintendo fighting game, Metal Gear series creator Hideo Kojima "practically begged" Sakurai to include the third-party character Solid Snake in Super Smash Bros. Melee as a playable fighter, but the addition was not viable because development of the game was too far in. As a result, no mention of Metal Gear reposes in the game whatsoever. What would eventually happen is that Snake would become a playable third-party character in Melee's follow-up, Super Smash Bros. Brawl.
 In Super Smash Bros. Brawl
Metal Gear debuts in Super Smash Bros. Brawl as the first third-party game series to feature in the Smash Bros. series, generating an outburst of excitement across the game industry.
When the first Brawl trailer was shown and Snake debuted, Hideo Kojima stated that Solid Snake wouldn't be able to fight Shigeru Miyamoto's Mario in the game, because it would be dishonorable for Hideo's character to beat up on his mentor's creation. Clearly that was a joke, as the Nintendo World 2006 trailer shows Mario smashing Snake out of the ring in one scene and was said to have fought against Mario in a match against Sakurai.
- Solid Snake: Solid Snake appears as a playable character, relying not on guns like in his games but on CQC (close quarters combat, martial art co created by Naked Snake in MGS3) and a variety of explosives, including his Remote Missile and Hand Grenade. Snake battles acrobatically and is seen using a punch-punch-spin kick fighting technique from the games, as well as his classic choke hold. He also seems to have a fantastic aerial recovery, thanks to the use of his flying camera, the Cypher. His Final Smash is the Grenade Launcher, which has him jump onto a passing helicopter and shooting players with 12 grenade missiles before the time runs out.
On the final character select screen (after all characters are unlocked), Snake occupies the ninth column (miscellaneous characters) along with Mr. Game & Watch, Sonic, and the random option.
 Assist Trophy
- Gray Fox: Gray Fox appears in his Cyborg Ninja form and attacks with a sword like Lyn and Samurai Goroh. His slices, however, can reflect projectiles.
- Shadow Moses Island: A stage set in the location where the first Metal Gear Solid takes place. It features searchlights, crumbling walls, and the appearance of three Metal Gear models. The stage also includes a feature that allows Snake to talk to his allies using his Codec, and have conversations with them about his opponents. To activate this, tap down on the the d-pad very lightly. This easter egg is much like Fox and Falco's special taunts on the Corneria and Venom stages. It has been said that Hideo Kojima designed the Shadow Moses stage himself.
- MGS4~Theme of Love~Smash Bros. Brawl Version - A fast-paced version of the Love Theme from Metal Gear Solid 4: Guns of the Patriots made for Super Smash Bros. Brawl. The arrangement was handled by staff from Konami's Metal Gear sound team. It is used on the Shadow Moses Island stage.
- Encounter - A remix of the song from Metal Gear Solid when Snake is spotted by an enemy. It is used on the Shadow Moses Island stage.
- Theme of Tara - A completely redone version of the Theme of Tara from the very first Metal Gear game for the MSX2. It is used on the Shadow Moses Island stage. For people familiar with Metal Gear Solid: VR Missions, this is the theme played when Snake is on a VR Mission in the game. It reappears in Metal Gear Solid 2: Substance, as another VR Mission theme for secret character MGS1 Snake.
- Battle in the Base - Taken directly from the PS2 game Metal Gear Solid 3: Snake Eater, this was the music track that played when Naked Snake was spotted by an enemy while indoors. It is used on the Shadow Moses Island stage.
- Yell "Dead Cell" - Taken directly from the PS2 game Metal Gear Solid 2: Sons of Liberty, this was the song that was used during the boss battles with Vamp, Fortune, and Fatman, who are part of the Dead Cell unit. It is used on the Shadow Moses Island stage.
- Cavern - Also taken directly from a title, this was the cavern background music in Metal Gear Solid. It is used on the Shadow Moses Island stage.
- Snake Eater (Instrumental) - An instrumental version of the main theme to Metal Gear Solid 3: Snake Eater, this track is also taken directly from said game. It is used on the Shadow Moses Island stage.
- Theme of Solid Snake - Taken directly from the MSX2 game Metal Gear 2: Solid Snake, the second game in the series, this was the title screen theme to said game. It is used on the Shadow Moses Island stage.
- Calling to the Night - The vocal theme song of the PSP game and direct sequel to Metal Gear Solid 3: Snake Eater--Metal Gear Solid: Portable Ops. It is taken directly from said game, and it is used on the Shadow Moses Island stage. This song also plays during Snake's Classic Mode credits.
- Metal Gear Victory - Snake's victory theme is the theme when you cleared the VR missions, but it is most known to be his game over theme from Metal Gear Solid.
 Games with elements from and in Super Smash Bros.
 Metal Gear
Solid Snake, the main character of the Metal Gear series, premièred in this game and is a playable fighter in Super Smash Bros. Brawl. Theme of Tara also originates from Metal Gear.
 Metal Gear 2: Solid Snake
Theme of Solid Snake, one of the two intro themes is an unlockable music track usable on the Shadow Moses Island stage.
 Metal Gear Solid
The Shadow Moses Island area from the game is a stage in Super Smash Bros. Brawl. Solid Snake's support team, Colonel Roy Campbell, Otacon, and Mei Ling appear in Codec transmissions in Snake's Smash Taunts. Gray Fox, a major character from the game, appears as an Assist Trophy. Metal Gear REX, Metal Gear RAY and the GEKKO also make an appearance as a part of the background in the Shadow Moses Island stage. Many Metal Gear Solid Characters also appear on stickers, such as that of Big Boss, Mei Ling, Solid Snake himself and the infamous Liquid Snake.
In turn, a reference to Super Smash Bros. Melee appears in the GameCube remake of MGS if the player has saved data for it on the Memory Card in use. Before the boss battle against Psycho Mantis, he will read Snake's mind (in actuality, the player's memory card) and note that Snake's played Melee before if data from that game is found.
 Metal Gear Solid 2: Sons of Liberty
Snake's intro animation resembles his appearence aboard the Discovery's aft deck wherein his stealth camo system disengages and malfunctions due to landing impact, as he had bungee jumped onto the tanker from the George Washington Bridge. Snake's Navy SEAL disguise "Iroquois Pliskin" is an unlockable trophy, as is Metal Gear RAY, and Raiden and Solidus appear as stickers. 'Yell Dead Cell, the "Plant" chapter boss theme is a usable music track as well.
 Metal Gear Solid 3: Snake Eater
Facially, Snake has a full beard similar to Naked Snake/Big Boss's appearence in this game, and his alternate colours consist of camouflage patterns used by Big Boss during the Virtuous Mission and Operation Snake Eater. Once in a while when using his C4 special move, Snake's C4 bomb may be shaped like a butterfly similar to when Big Boss molded a C3 explosive into a butterfly before placing it on the Shagohod's fuel tank. Naked Snake appears as a trophy, as does the Shagohod, MGS3's equivalent to a Metal Gear, and EVA and The Boss appear on stickers.
 Metal Gear Solid: Portable Ops
Calling to the Night, the game's ending theme, is an unlockable theme in Brawl. Gray Fox also appeared in this game, as "Null", a soldier engineered to be "perfect".
 Metal Gear Solid 4: Guns of the Patriots
Theme of Love is usable in Shadow Moses and is a remix of this game's main theme. Metal Gear GEKKO also appears as a trophy and a background element in the Shadow Moses stage.