For U.S. Citizens: You are able to purchase ETH directly from your MetaMask wallet using the Coinbase widget. Just click the ‘Buy’ button to get started. You can follow a step by step process we’ve documented here for setting up Metamask to purchase cryptocurrency. https://medium.com/emusic-official/the-emusic-guide-to-buying-crypto-88b2d64bc55
For everyone else: to buy ETH from Coinbase you need to be located in one of the countries they support. Please go to Coinbase.com and double check that you are able to buy in their website before using the Coinbase Buy Widget integration. If you cannot buy at Coinbase.com, you will need to find another exchange or service were you can buy ETH in your country with local currency. Then, you will be able to send any ETH or ERC20 tokens to any of the receiving addresses of your MetaMask wallet.