Yes, you can log in without a password if you have Automatic Login enabled on your Mac: go to System Preferences > Users & Groups. Click the Lock to make changes and go to Login Options. Click ‘Automatic Login’ and choose the account you want to log into without a password. Confirm your intention by typing its password. Now, it’s password-free.
Note that Automatic Login is disabled in case the account uses iCloud to log in, or you have FileVault enabled on your Mac. Each of these helps ensure your Mac’s security, so we don’t recommend disabling password-protected login.
Tip for Apple Watch users: If you want to keep your Mac login secure but entering password is just too tiresome for you, set your Mac to unlock with Apple Watch: System Preferences > Security & Privacy > General > Use your Apple Watch to unlock apps and your Mac. From that moment on, if your Mac has Bluetooth and Wi-Fi on, and your Apple Watch is nearby, the Mac will unlock automatically!