In the beginning was the Word, and the Word was with Sabbath, and the Word was metal. Metal's prophet, Ozzy Osbourne, pondered long and heard how best to bring the metal to the masses. One day through dream did it hearken unto him: "MY child, you must shod yourself with a mighty axe, rollicking thunder, and turn the amp up to 11!" Verily, Ozzy did comply, and the Word was good.
Upon hearing the music, the people were shocked and became calamitous. Ozzy Osbourne was pleased, as an inherent tenet of Metal is to not give a fuck. He was so pleased that he shot two hits of cocaine.
The elders of the Western World were greatly concerned. They did not know what an "Iron Man" was, but they knew the sound was music of dark gods, and lo did they gnash their teeth and rent their clothes asunder.
Other bands came aboard the locomotive force of distortion and brash vocals, and thus was Metal borne on the waves of epic destruction.