Can I connect a iPhone to Metro PCs with a $40 unlimited plan?

I want to connect a iPhone, I don't really care which version aslong as I can get at least the iPhone 4. Also, will I have to buy an unlocked one? Or could I just connect any iPhone to it?

No actually you can't use an unlocked GSM iphone with metro pcs. A Sprint iphone may work, it requires something calling flashing your phone. You can get unlimited for $40 w/ H2O wireless, it uses AT&T's network