Connecting a Ledger to MetaMask lets you use the Ethereum ecosystem and DeFi apps while keeping your keys on the hardware wallet.
Install the MetaMask browser extension or mobile app and complete its basic setup.
On your Ledger, open the Ethereum app and enable the setting that allows it to communicate with MetaMask.
In MetaMask, choose the option to connect a hardware wallet, select Ledger, and follow the prompts.
Choose which Ethereum accounts you want to use in MetaMask and import them.
Every transaction from MetaMask must now be approved physically on your Ledger, keeping your keys safe.
This combination gives you the convenience of MetaMask with the security of a hardware wallet.