Just bought a used iPhone 4 from ebay?

The product says: You are bidding on an excellent condition Apple iPhone 4 - 8GB - White (AT&T)

The front screen has a small crack at the top right corner and the bottom right corner, but is in good condition otherwise. The back is in great condition with only some small scuffing. The metal rim is in good condition except for some small scratching. The volume, home and lock buttons all work perfectly. Overall the phone is in great condition if you don't mind the cracks in the front screen.

This phone has been reset and has a clean ESN, so its ready to go. It also has iCloud lock turned off. We ship all items within 24 hours, good luck bidding and don't hesitate to ask any questions.

I want to use it on Metro Pcs. How can i do that or if the phone does not allow me to do that what other carrier beside AT&T would work? Maybe straight talk?

MetroPCS says that the AT&T iPhone 4 is compatible with their network by using the $10 sim card.

You Simply Get the phone-Buy the sim card-activate the sim card

Be sure to visit the MetroPCS store for help if needed.

Hope this works, Enjoy your phone!