Best Heavy Metal Band of all time. (Do people still listen to metal?)

Who was the first heavy metal group? Some historians claim Led Zeppelin with the release of their
first album released in Jan. 1969. Imo, it was Blue Cheer who released the first album in Jan. 1968.
Their only hit was a remake of Eddie Cochrans Summer Time Blues. They also had the reputation
as the loudest band. Concert goers would often leave the first rows when they played.