When did heavy metal music begin?
Heavy metal developed in the late 60s and early 70s largely in the United Kingdom.  Part of the British Invasion.
Did Led Zepplin lead the way?
Zeppelin, Black Sabbath and Deep Purple were all founded in 1968
Who was the bass player in Zeppelin?
The bassist was Robert Plant.  Keyboardist John Paul Jones.
He also sang most of the songs, right?
Yes Robert Plant sang