Metal Cap

The Metal Cap is an accessory that makes its debut appearance in Super Mario 64. It is usually found in Metal Boxes. The Metal Cap can turn Mario into Metal Mario, which makes him invulnerable. The side effect of this temporary invulnerability is that the user becomes extremely heavy (with a side effect of extremely powerful Ground Pounds), they can no longer make very high or long jumps, and they sink faster in quick sand. Also, when Wario gets a Power Flower in Super Mario 64 DS, he becomes Metal Wario, which has the same properties as Metal Mario.

A similar item, the Metal Mushroom works almost identically to the Metal Cap.

The Metal Cap's ! Switch can be found in the Metal Cavern, which can be reached by a portal in Hazy Maze Cave's underground lake area.

The Metal Box also appears in Super Smash Bros. Melee and is also present in Super Smash Bros. Brawl.