Fact is they were called heavy metal when their albums were out, with the exception of the pre In Rock Purple albums.
If we keep redefining metal, it wont be long before Priest themselves are redfined. In Rock and Machine Head are much heavier, and better than Rocka Rolla. Ditto Gypsy
Exactly. I'd even say that Deep Purple (and to some extent Uriah Heep) are more important for
heavy metal than Sabbath (which I love the most of the three bands).
While Sabbath's music was absolutely heavy and groundbreaking, Purple were heavy AND fast. Sure, maybe not as heavy as Black Sabbath, but heavy metal isn't just about heaviness. It's about melodies and speed too. Look at Mercyful Fate and Iron Maiden, one of the most definitive heavy metal bands. They're not direct heirs to Sabbath, but to Heep and Purple (and in Mercy's case, Priest). The high vocals, the fast tempos, the bass lines... In Rock is where it all began. So is Demons & Wizards, Very 'Eavy, and some other LPs. Sabbath weren't
heavy metal until Heaven and Hell, when Dio's presence allowed Iommi to try some new things. They were a very experimental band, they were a doom/stoner metal band, but not a
heavy metal band. Of course, they did write some songs that can easily be considered heavy metal (such as Killing Yourself to Live), but most of their classic tracks are the ultimate stoner/doom songs. And then you have Accept, who didn't sound like Sabbath at all, more like a mix of Priest and AC/DC. On the other hand, bands such as the iconic Pentagram, were never ashamed of their Black Sabbath obsession and had very little to do with other early 70s bands.
I'd say that
heavy metal as a real, standalone genre started in 1977 with Rainbow's Rising and Priest's Sin After Sin. Nowadays calling the Mk. II records heavy metal may sound controversial, but they were crucial to the evolution of heavy metal, and it's hard to imagine how the metal scene would have looked today if there had been no Highway Star, Easy Livin', or Fireball.