Erm......perhaps you should put this in the computer games section. But anyways meatal enemeys are always, lets just say "jerks" simple trick. just throw them there not worth trying to damage and they fall to fast.
The fighting polygon team is MUCH harder to beat without losing stock on "Very Hard".
Metal Mario can cause problems, but if you stick to a strategy of attacking with your longest reaching moves and then running away before he hits back, it's not all that hard. Remember: the downside to Metal Mario's "metal-ness" is the fact that he's slower than Dick Cheney disclosing secret torture programs.