What is OpenSea? This is the primary question that clicks in our minds. It is the largest marketplace for trading in NFTs. There are several wallets available in the cryptocurrency market. And, we will learn how to link the MetaMask wallet to OpenSea. If you are looking to trade into NFTs on OpenSea, you can do it through the MetaMask wallet. MetaMask sign in becomes necessary if you want to buy, sell and share the non-fungible tokens.