after you beat metal madness yo have to defeat it with team chaotix. Heres wut yo need to do:
1. get charmy on lvl 2
2. the boss must have only 1-3 health
3. get espio and vector inside the crystals (wut the boss is shooting from its hands)
4. when yor alone with charmy, jump (DONT FLY) and in midair press  button repeatedly (charmy should sting it with his spike on his butt) and yo have to hit the boss into its weak spot)
5. the boss dies and charmy drops down to his death =(
6. then yo should be in the edge of the place yo was fighting in
7. fly to the place on yor left (that has boxes) its the place you normally should be fighting with team dark
8. kick some metal ass of metal sonic (on otherwords: kill him)
9. he dies and yo did the part of team dark with team chaotix!
ps. take many many lives with yo coz u may die in that
psps.it sometimes works, sometimes not.