I really and respectfully have to disagree, when Led Zep first appeared they were mainly out of the blues strained through England's vision of American bluesmen. In the day we NEVER referred to them as heavy metal, they were 'Led Zeppelin'. I honestly think they were not even pioneers of the genre (heavy metal), true, they could rock out. I would put the linage on Steppenwolf, Deep Purple etc eventually Sabbath who really nailed it down. I do not, will not argue and no snark intended. It does make for a great discussion, this is the view of someone who was 16 or so when Zep hit. One of the first 'genres' I can remember was when no one could classify the Eagles (Burritos, Parsons etc) and it was designated as 'country-rock'. Silly people. Trix are for kids. Hell, I remember buying a Led Zeppelin record and a Micheal Nesmith and the First National Band record on the same day. PTOO on genre. Dig the MUSIC.