MetaMask accounts automatically generate a Stellar network address derived directly from the user's existing secret recovery phrase without requiring separate network setup.

From the articleMetaMask makes Stellar a default network, bringing global payments into the Open Money platformAlso in MetaMask Makes Stellar a Default Network on Mobile and Extension, Stellar joins MetaMask: What the wallet update brings to XLM users - AMBCrypto, Stellar Added to MetaMask’s Default Supported Networks