By default, both MetaMask Institutional and production MetaMask connect to the Ethereum blockchain network. But MetaMask is, by design, open and flexible. Just as you can browse computer networks all over the world with your Web browser, MetaMask can access many different blockchain networks, and you choose which one you're on by clicking the drop-down menu at the top of your MetaMask window:
Adding a Network
If you don't see the network you need in the list, the simplest way to add it is by searching for it on Chainlist and clicking 'Connect Wallet'.
If the network isn't available on Chainlist, or you need to manually configure the connection points to the network, or you want to be double-sure the network you're connecting to is exactly the one you mean to connect to (provided you have the correct endpoint information), follow the instructions here in production MetaMask's support documentation to manually configure the network.
For more information and helpful tips on working with custom networks, keep in mind the User Guide here.