Magic Keyboard
The wireless Magic Keyboard included with your iMac has built-in features that make it easy to enter emoji, switch keyboard languages, lock your iMac, and perform many system functions with the touch of a key. The Magic Keyboard with Touch ID also lets you use a fingerprint to sign in and make purchases using Apple Pay.
To connect your Magic Keyboard to your iMac, see (Magic Keyboards that don’t have Touch ID have a Lock key instead). To unlock your iMac, lightly touch Touch ID, or press any key and type your password.
Set up Touch ID. If your keyboard has Touch ID, you can use your fingerprint to unlock your iMac and make purchases from the App Store, Apple TV app, and Apple Books, and on websites using Apple Pay. If you don’t set up Touch ID when you set up your iMac, you can do it later in the Touch ID & Password settings in to switch to a different keyboard. Press 
Spotlight Search (F4): Press 
Media (F7, F8, F9): Press 
Volume (F11, F12): Press 
Note: Touch ID and the function keys work as described above for any Mac with Apple silicon and macOS 11.3 or later.