I don't see how Sabbath aren't considered metal.
Well let's talley em up on the good ol' 'Checklist a la Metal from hell' shall we?
Doom-ey, HEAVY riffage? Check.
Satanic/controversial lyrics? Check.
Major influence for EVERYthing that IS and ever WILL be metal? Check.
Solos? Triple-check.
Was Ozzy Osbourne ever in the band? Check.
Elaborately evil and dark atmosphere in terms of stage show? Check.
Yes folks, I believe what we have here is a good old fashioned Heavy Metal band, I reckon, yepyep!