NFTs in the Portfolio Dapp
Have you heard about the MetaMask Portfolio Dapp? It displays all your NFTs in a consolidated portfolio view, and may mean you don't need to add them to MetaMask at all.
Give it a try at portfolio.metamask.io or click the link from MetaMask Extension.
ERC-1155 tokens are supported by MetaMask Mobile and Extension, meaning your wallet can receive and store assets aligned with this token standard.
Images associated with these assets are also visible on Mobile, and we are working on extending this functionality to Extension.
MetaMask does not yet support sending your ERC-1155 tokens, although we're working to implement this feature soon. In the meantime, we recommend you use a platform that supports ERC-1155 transfers, such as OpenSea.