Lets say you are battling with an Arceus that is holding a Zap Plate, making it a Electric type. What would happen to it if someone used Knock Off, Thief,Trick,etc to take away that plate. Would it stay an Electric type or would it go back to Normal type.
If any item item related move (trick, knock off, etc) is used on an arceus holding an elemental plate, it will fail, as the ability multitype makes it so that Arcues can't lose it's plate. Therefore it would stay an electric type.
Credit to uberpwnage