Something I say here and there to my students is “guitar playing is a lot of the same things a lot of the time.” The act of playing the guitar is made up of a lot of the same techniques.
If you get comfortable with one of these techniques in a certain song or solo, when you come across it in any other song or solo – you’ll be OK with it.
Also – rock, blues and metal guitar are all made up of a lot of the same musical concepts.
If you need to become comfortable with a certain scale or key when learning a metal song, you’ll be able to capitalise on that knowledge and previous practice if you learn another metal song in the same key using the same scale.