Motorhead. No matter if you love 'em or hate 'em, you can't deny their influence on metal and hard rock in general over the past three decades. After leaving the space rock band Hawkwind in the early mid 1970's, Lemmy came foward on his own in full force with Motorhead. With a biker image, blazing fast tempos, deafening guitars and growling vocals, biker metal was born, and rock and roll became exciting again. Not until the insurgence of punk in the late 1970's would there be anything that approached their energy.
Here's one of my favorite tracks, the classic "Ace of Spades".