Effect
Raises Defense of Ditto. (Hold)
Metal Powder is a Ditto item only that will double its Defense stat! That being said, this only works on Ditto specifically, not on the Pokémon it transforms into. So its only useful for the first turn.
I'll be honest, I don't know many people who run a Ditto. Also, once Ditto transforms, it loses the Metal Powder boost anyway, so the competitive use is extremely limited.
Game:Polished Crystal