From the Coinbase app: Open the mobile app, and click on “Portfolio.” Find “Ethereum,” and select “ETH Wallet.” You should see your balance here. To send ETH to your wallet on MetaMask, click on the send icon in the top right. Enter the amount of ETH you want to send and click “Continue.” In the “To” field, paste in your Ethereum wallet address. Click “Preview” to confirm the amount and once you’re ready, hit “Send Now.” Wait a few minutes for the ETH to arrive in your wallet.