NFTs can be viewed via the mobile version of Metamask. Users can also add NFTs as custom tokens in the web extension.
MetaMask Mobile displays NFTs under “Collectibles”. If an NFT is not displayed by default, do the following:
Click on the NFT "Contract Address".
From the Etherscan at the top-right of the page you can find the address of the contract that created your NFT. Copy that address
From the MetaMask Mobile wallet, click on the “'NFTs” and then click on the "+ ADD NFTs" link. Paste the NFT address into the "Address" box.
Copy the ID of your NFT under "Details" on the NFTs listing page on Swappable.
Paste the ID into the box "ID" in MetaMask Mobile, tap on the "ADD" button, and your NFT should appear under the NFTs tab.