ARMS contains a total of 42 different ARMS. Any character can use any ARM but they must be unlocked individually for each character. Each character starts with 3 ARMS unlocked, and new ARMS are obtained in the Get ARMS mode. If the player obtains an ARM that a character already has, it becomes the "plus" version of that arm. There are thus a total of 570 unlocks in the game currently.
The weight of an ARM determines its use in countering other ARMs. If an ARM strikes a heavier ARM, the lighter ARM will be stunned. If an ARM strikes an ARM of the same weight, the ARM that was activated later will be stunned. This means that you can strike opponent's punches out of the air with ARMs of the same weight or heavier than the opponent's. Note that this only applies to punches. Grabs can always be struck out of the air regardless of the weight of the ARMs being used.
The elemental setting of an ARM determines the effect it has on the opponent if it hits while charged. Uncharged ARMs do not apply their elemental effects, but still do damage.
- Blind: makes a blob appear on the opponent's screen, covering a substantial part of the centre area for a few moments.
- Electric: if it hits, stuns both the opponent's ARMs and prevents them moving for a second or two, giving an excellent opportunity to land a grab.
- Explosion: causes an explosion after the initial attack, even if the initial attack was blocked. This can trick the opponent, but it can also harm you.
- Fire: does additional damage and knocks the opponent down.
- Ice: slows down the opponent's movement dramatically and prevents them jumping for any significant distance.
- Stun: stuns the opponent very briefly on impact. Does not provide a long term stun in the same way Electric does.
- Wind: knocks the opponent into the air.
- Poison: Inflicts damage over time. It will increase with consecutive hits