Its hard, really, to draw definative boundaries based solely upon chronology.
Alice Cooper would probably be the first to have reached the Metal monikers, but he was very closely followed(and independantly) by the likes of Yardbirds, Cream, Spencer Davis in the '60’s.
Most of these earlier groups would probably considered themselves as heavy rock, or taking the R & B genre further on down the road.
Led Zepp were certainly a blues based outfit, Clapton, and most other notable electric guitarists took much of their inspiration from blues, especially from folk like Howlin’ Wolf, Muddy Waters and John Lee Hooker.
I personally think that heavy metal was a development of R & B that took further on where the Rolling Stones stopped short.
Old Heavy Metal bands would be Deep Purple, Sabbath,Coliseum Wishbone Ash, Uriah Heep, some of this would border on to progressive rock with bands such as the Nice.
Metal is to me moving further from those older Heavy Metal bands into the hyper fast guitar hammering style such as Metallica, Megadeath and the old R & B roots have all but dissapeared.
Power Metal is also known in the UK as ‘Cock Rock’ of ‘Hair rock’ with bands like Boston, Kansas,Styx, and Toto being the exponents.
Unless your opinions vary.
To me bands such as, AC/DC, and Iron Maiden have a no-nonsense pretty basic approach to music and are maybe closer to rock and roll than blues in origin.
Then you get on to things like Free, Bad Company, UFO, Krokus that don’t fit neatly into these but are still very much hard rock.
Limp Bizkit, whilst being loud enough, do not belong to any of these groupings, and Comcast classification of Metallica and Iron Maiden are well out of it, as they don’t really belong in the same sub-genre and would not belong in the power Metal genre which would include Rainbow, and Whitesnake, and the middle to later period of Black Sabbath.
(Power Rock? Wtf…)
