Perhaps I shouldn't be the one answering this, but that has never stopped me before. I can think of Eric Clapton's "Crossroads." He switches between Amaj and Amin. First off, if you are playing Roots and Fifths (power chords), you can play major or minor sclaes over it because you don't have a 3rd to interfere.
Moreover, if you are playing over a G-C-D progression, you can
play a G scale ove rthe entire piece, but you can also play over the C (or the D) out of that scale if the notes are not dissonant to the C (or the D).
I am sure somebody could write a whole bunch more. Perhaps you need to ask a teacher in another lesson.