Pressing and holding the special move button once will cause Snake to pull out the pin of a grenade on frame 1, and releasing the button (or pressing the attack button) will cause him to throw it. Snake can walk back and forth, jump, and midair jump while holding a grenade, all while facing the same direction he was in when he started the move. The distance that Snake throws the grenade depends on how the control stick is tilted while releasing the button. Snake can only have up to two grenades in play at a time; no more can be produced until one of them is thrown offstage or explodes.
The grenade detonates 3 seconds (2.5 in Ultimate) after Snake pulls the pin (as indicated on the grenade itself), and Snake can be damaged by his own grenade if he is still holding it or is too close to it when it explodes. Unlike Young Link and Toon Link's bombs (and Link's prior to Ultimate), it does not explode on contact, and any fighter can pick it up before it explodes. If an opponent is physically hit by the grenade before it explodes, they will receive 1-5% damage, but it will never cause the opponent to flinch. The grenade's explosion inflicts around 12% damage (9% in Ultimate) with decent vertical knockback.
If Snake is close to a grenade when it goes off, he will cover his ears from the noise of the explosion. Kirby will also do this if he copies Snake (even though he has no visible ears).
The grenade's delay time can be exploited by "cooking" it – that is, holding the special move button (as it is only thrown when the button is released) to reduce the time between the moment it's thrown and the moment it detonates. Not only does this add an element of unpredictability when using grenades, but doing so also makes it more difficult for enemies to dodge or throw back the grenade.
Grenades are also unique from the Links' bombs or Peach's Vegetables in that they take priority over held items; Snake can still perform the move while holding an item, and anything he carries will be dropped as soon as he presses the special move button.
Interestingly, the Hand Grenade cannot be held while shielding, and attempting to do so will cause Snake to drop the grenade at his feet. This can be used in various ways; for example, it can be a defensive measure by shielding and dropping the grenade to Snake's feet when an opponent attacks. Not only will Snake block their attack, but the explosion will damage the opponent and not Snake because he is still shielding. He can also quickly drop the grenade and then pick it up to throw it in a more traditional way, or dodge an incoming attack while holding a grenade, which will leave the grenade behind and likely be set off by the attacking player. In Brawl, this also makes any of his grenades that are being carried or even thrown by another player fall straight down. Snake can quickly shield after pulling out a grenade then repeat it again, and can throw both grenades quickly at an enemy and explode each one in the process. The blast radius will be very large and will inflict around 25% (18% in Ultimate) from both grenades. This must be done quickly because dropping and picking the grenades takes two seconds and must throw the first grenade immediately followed by the second. Snake will always pick up the grenade that has been out longer.
Grenades can be used to ameliorate Snake's aerial mobility, which is one of the worst in the game due to its sluggish nature. Snake can B-reverse in the air when taking out a grenade, changing the direction that he faces and shifting momentum in the opposite direction. This can be used to mindgame opponents, who expect Snake to fall in a certain pattern downwards or on a certain section of the stage.
In Brawl, Meta Knight and Kirby can also perform the Omnigay on a Snake holding a grenade if they have the higher port, which usually causes instant death for the Snake while the other character survives.
Hand grenades have been a staple offensive tool in the Metal Gear series ever since their introduction in Metal Gear 2: Solid Snake. They can easily be found in lockers, store rooms, or obtained from enemy soldiers.