My brother loves heavy metal music, it was developed in the late 1960's, early 1970's
I dont know very much about it, I think I may have heard it before. 
It has roots in blues rock and psychedelic rock.
I understand, who are some famous bands or artists of that Genre?
Led Zeppelin, Black Sabbath and Deep Purple are the 3 most popular original heavy metal bands.
Oh okay I know who Led Zeppelin is! What are some of the number one hits of the genre?
I'm not sure, but in the late 1970's, there was a new wave of heavy metal and bands like Iron Maiden and Saxon became popular.