Electric guitar...

C, D, and G are the "weird" chords that don't have the same shape as the "Black Sabbath" barre chords, or their open equivalents.

You can also do a hell of a lot of rock and roll with just E and A and barre's.

...and palm muting. Learn palm muting. Must. Quiet the strings you aren't playing.
Instantly makes you sound much better, once you get that down.