Google has just announced that MetroPCS now supports Google Wallet, marking the first major expansion of the service in terms of carrier support. So far Sprint has been the only carrier to support Google Wallet — AT&T, Verizon, and T-Mobile are busy promoting their own ISIS network, which just launched today in Austin and Salt Lake City — but Google's solution already has a leg up on some competitors since it has already rolled out nationwide. Google's tweet announcing MetroPCS support mentions that Galaxy S III owners on the carrier can get started with the service right now.