Metal Box

The Metal Box is a green block with an exclamation mark on it. It is an item that originates from Super Mario 64. In the Super Smash Bros. series, the Metal Box appears as an item in Super Smash Bros. Melee and later installments. When used, the Metal Box temporarily coats its user in metal, although unlike its originating game, the Metal Box does not release a metal cap. Giga Bowser, Wario-Man, Mega Lucario, and Giga Mac are unaffected by Metal Boxes.

Trivia

 * In Super Smash Bros. for Wii U, the trophy states the Metal Box appears in Super Mario 64 DS, but that game replaced the colored caps with multiple characters and their Power Flowers are all found in red ? Blocks.