Reading people who don't really listen to much Metal ideas on what constitutes an early Metal song is like reading a description of the taste of chocolate by someone who has never tasted it.
It takes more then speed and a bit of distortion on the amp to make a song, Metal.
Metal has a more sinister element / attitude / atmosphere and generally invovles a more down tuned sound. Plus a complexed element of a Progressive Rock , Jazz and Classical nature,
example; Geezer Butler & Bill Ward's almost swing time , Progressive Jazz, rhythm section which, are the back bone of Sabbath's songs. Combined with Ozzy's eerie, sinister, vocal style and Tony Iommi's down tuned, distorted, doom ladened, guitar riffing ....a newly crafted ( at the time ), horrific element was added to Rock & Roll , which combined to give birth to the Genre : Heavy Metal.
There are many musical components that make Metal what it is. It is not just distortion, loudness, and speed ....
Anyone, who doesn't understand these FACTS, is ignorant to what musical elements make up the music form refered to as, METAL.
And this overview hasn't even touched upon the non- conventional strutures that much of Metal incorporates, or the tendency to have a multitude of time changes / sigintures. ...