You can unlock your Android phone even if you've forgotten the passcode, but you'll usually need to factory reset the phone.

How to Unlock Android Phone Pattern Lock without Factory Reset: If you’re using an Android device running version 4.4 or earlier, you can use the “Forgot Pattern” option to unlock your phone ...

Google has announced the ability for people to use their Android phone as a hardware security key, allowing you to securely authenticate your access.