When activated, Meta Knight spins at high speed and surrounds himself in a dense yellow tornado that covers a majority of him for a set period of time, which can be extended by mashing the special button; mashing also causes Meta Knight to rise up vertically. More vertical distance is gained if the player simultaneously jumps and performs the move. Mach Tornado can be controlled by pressing left or right to move in that direction. Once the move ends, Meta Knight falls helpless.
The tornado causes a slight pull on nearby opponents. Enemies that touch the tornado are trapped, slashed multiple times, and then sent flying with a final hit that deals moderate knockback. The move is hard to escape via directional influence, and the final hit deals moderate knockback, making it an effective KO finisher if enemies are near the top blast line.
Brawl's version of Mach Tornado grants a significant amount of aerial mobility, making it one of the best recovery moves in the game; in addition to granting high horizontal distance, it travels a good distance vertically and can be made to change directions quickly. Furthermore, the move possesses near instantaneous start-up lag, and has multiple large hitboxes that can clash with ground and aerial hitboxes (including projectiles, so long as they deal 9% or less and/or do not possess transcendent priority). With all these considered, Mach Tornado is often considered an extremely safe and effective move when regarding its overall recovery and offensive potential.
The move is not completely infallible, however; Meta Knight will bounce off edges rather than grab them during the move, and is additionally unable to grab edges during the first few frames of his helpless animation. This can potentially cause a self-destruct if the move is mistimed. Additionally, missing and ending the move near the top of the screen is punishable, and Meta Knight receives an additional 20% knockback if he is hit out of Mach Tornado.
The mobility and damage potential granted by Mach Tornado makes it one of the staple finishing moves of the Rufio combo, especially against fastfallers.
Mach Tornado returns as Meta Knight's neutral special move in Smash 4. Unlike in Brawl, Meta Knight simply cloaks himself in yellow winds instead of a solid tornado.
With the reduced effectiveness of Directional Influence on multi-hitting attacks, Mach Tornado retains its effectiveness at trapping opponents and dealing high damage (compared to the majority of Meta Knight's attacks), in addition to having higher base knockback on the final hit. However, the move's duration and mobility have been nerfed considerably; it lasts a much shorter amount of time unless the player button mashes, and its reduced horizontal and vertical mobility give it more limited use as a recovery (vertical movement is especially affected). This is further burdened by the move being unable to edge sweetspot for its duration until Meta Knight becomes helpless.
Offensively, Mach Tornado's hitbox placements are arguably worse; when including its higher ending lag and the removal of transcendent priority throughout Meta Knight's moveset, this prevents the move from being a solid invincibility option and makes it easier to punish. The aforementioned reductions to the move's mobility also prevents Mach Tornado from functioning as an effective finisher for the Rufio combo.
Overall, Mach Tornado now functions mainly as an out of shield move, typically used as a punishment option to rack up significant damage, due to it dealing much more damage compared to the rest of his attacks.
Mach Tornado returns as Meta Knight's neutral special move in Super Smash Bros. Ultimate. Unlike in the previous games, Mach Tornado hits only once, instead of being a multi-hit attack. It also travels at a faster pace, giving it much better horizontal movement compared to previous games. It has considerably more knockback than before, being a potent kill combo finisher.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Control-wise, this move is like Kirby's "Tornado" ability that appears in many of the Kirby games. Holding B will make him gain height. Meta Knight first used it in Kirby Super Star, where he transformed into a yellow tornado to attack. In the actual Kirby games, Mach Tornado refers to an attack that he (and Dark Meta Knight) uses where he flies to the side of the screen and launches a gigantic tornado towards the other side of the screen by charging and then stabbing his sword to the ground.
In Kirby Super Star Ultra, Meta Knight stars in his own mode, Meta Knightmare Ultra, which involves him replaying various levels from other sub-games. In said game mode, defeating enemies would allow him to gain points to perform various special techniques. The strongest technique is also named Mach Tornado, but is instead a screen-clearing attack similar to a Final Smash, instead of a small tornado. As Kirby Super Star Ultra was released after Brawl, it's likely that the move was named after Meta Knight's neutral special.
Kirby: Planet Robobot also names his variant of the airborne Twister Slash technique Mach Tornado, though his grounded version features the yellow trail commonly associated with the move.
Meta Knight also has a move in Kirby Star Allies known as Mach Tornado, though it's identical to his Twister Slash move from Kirby: Planet Robobot.