Electric guitar...

BTW- that I, IV, V pattern mentioned above (for the OP, that's basically "Louie, Louie" or "Wild Thing") can also be done with all "Black Sabbath" chords and it's way easier and faster to play that way to work on timing and palm muting, although it doesn't ring out the same as the open, full chords.

Some songs call for it one way, some the other.

I'd suggest practicing both ways and seeing if you can seamlessly switch between the two while staying in time. That's a great exercise that's not too terribly difficult that builds reps in several areas.