Metal Box

The Metal Box is a green ! Block appearing in Super Mario 64. By breaking it, Mario is able to get the Metal Cap. The switch to turn on the Metal Boxes is located in the Cavern of the Metal Cap, a secret area inside Hazy Maze Cave.

The Metal Box also appears as an item in Super Smash Bros. Melee, and returns in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U. When used, characters become coated in Metal for a short period of time, but also become much heavier, which means it is harder to KO them by blasting them away, although they fall much faster, making it harder to get back on the stage. Also, the voice of the character who is in use with the Metal Box is not heard. In Super Mario 64, however, Mario's voice is heard. Underwater, his voice is not heard unless he is falling from a great height. Additionally, a trophy of the Metal Box appears.

On a side note, Giga Bowser, Wario-Man, Mega Lucario, and Giga Mac are unaffected by Metal Boxes.

Super Smash Bros. for Nintendo 3DS / Wii U
Blue indicates exclusive to the Wii U version.