When the special move button is pressed, Wario opens his mouth and bites forward. The bite itself is non-damaging, except against the Subspace Army; something has to go in Wario's open mouth for the move to have any effect. Another method he can do with this technique is to hold the special button and Wario will keep his mouth open for longer. This acts as a grab, and can hit shielding enemies. If the button is held down, his mouth stays open briefly, making it possible to grab anyone who moves into range. While grabbed, Wario can bite by pressing the special move button, dealing a small amount of damage each time. The higher the enemy's damage, the more times Wario can bite. This can also be used to block Snake's recovery instead of taking a bit of damage.
Chomp can also be used to eat items and projectiles, up to 3 if Wario is close enough. Wario can do nothing and simply swallows the projectile or item. Eating a large item, such as a crate, takes longer to swallow and leaves Wario more vulnerable. If it's a status or recovery item like a Superspicy Curry or a Heart Container, Wario will immediately gain its effect. Explosive items like a Bob-omb are damaging to Wario, dealing 6% damage, but damaging anyone in blast range. Any object that can be picked up (Link/Snake's bombs/Hand Grenades, Peach's Turnips, Diddy Kong's Peanuts/Banana Peels, Waddle Dees/Doos etc.) can be eaten by Chomp. The three exceptions to this are Mr. Saturn, Poké Balls (as well as any holdable Pokémon inside; both Mr. Saturn and Pokémon themselves are also living beings), and the Smash Ball (which can't be picked up with a single button press).
In Super Smash Bros. 4, the Chomp attack has received a number of changes. Eating items and projectiles from items (such as the Ray Gun's projectiles) will now heal Wario by 1% each. Items that heal the player also increase Wario's Waft charge. Also, Wario can now eat energy projectiles such as Mario's Fireball, but he does not heal or get any Waft charge from eating them. Finally, eating food items will heal him more by 1.5x the amount it would normally heal him (e.g. eating Maxim Tomatoes will heal 75% rather than 50%).
Super Smash Bros. Ultimate introduced some more changes, as Chomp heals Wario when he bites down on someone along with enemy projectiles. It was also given significantly more knockback, now capable of killing opponents at high percents near the ledge.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Besides Wario's love of eating in general, the move is very loosely inspired by the microgame Hot Dog Hog from WarioWare, Inc.: Mega Microgame$! where Wario has to finish chomping on a long hotdog to win the game, or Eating Contest from WarioWare: Twisted!, where a player must finish the minigame by eating a watermelon, a banana, or a doughnut.
Garlic Breath is inspired by Wario's love of garlic.