You can now use a physical security key to log into Facebook on Android and iOS
In case you aren't sure what factor-authentication is, it's a security feature which requires proof by asking for something only you know (your password) and something you have (such as a text to your phone).
Facebook suggests public figures or celebrities might stand to benefit most from incorporating a physical security key into their accounts, as they are at a greater risk of being hacked—although anyone who could be bothered to use such a key would benefit from essentially guaranteed account safety.
Although Facebook doesn't sell hardware keys, you can always purchase them from a third-party hardware store such as Micro Center. The keys can work both through Bluetooth and by directly connecting it into your phone's charging port.
To set up a security key in your Facebook Account, you simply have to go to Two-Factor Authentication within the Security and Login section of your Settings and enroll it there. You can go to Facebook's official post for more information here.