Is iPhone 4s compatible with metro pcs?

I'm pretty sure it is if it's unlocked but I don't really know how to go about buying it. I checked around online and many places seem distrusting and the apple store seems expensive. I need a phone that can carry a gsm supported SIM card to connect it to my plan and right now I'm looking at $450 and that doesn't look right

If your budget is $450, you'll get iPhone 5C new and without contract. I would suggest you to get that and unlocked iPhone will surely work on MetroPCS. If you need unlocked iPhone cheaper than retail, mail me.