Here’s how to buy ETH in MetaMask
Open the MetaMask mobile app, and make sure you’re on the Wallet page.
Choose a payment method. (You can enter your credit/debit card number for all three options.)
Enter the amount you want to buy
If you’re going to be on the Whitelist, buy at least 0.07 ETH. If you aren’t on the Whitelist, buy at least 0.12 ETH. (NOTE: This screen will be different depending on the payment method you choose.)
Here is the confirmation