A Burzum fan attempting to tell anybody what is and isn't genuine metal? lolz, anyway, no Black Sabbath weren't the first heavy metal band, they were one of the first, and certainly the first to make it popular on a larger scale with high charting positions., this is why they are often credited as the first... though bands such as Blue Cheer predate them. I'm guessing you are 15 or 16 now, so you certainly werent around in the 1970s to experience the movement or understand what it was about, etc. 

 Angst ridden whining, claiming metal doesn't have anything to do with the mainstream is pure ignorance of the historic factualities of metal and its widely spread chartings from around the time it began (as showed in the Sabbath link), to bands from its subgenres charting highly even today; Iron Maiden's latest album has charted nationally at #9 in the US, #4 in the UK, #2 in Canada during 2006.... thus proving metal is and always has been a mainstream form of music, your obscure cookie monster music bands may not be mainstream, but then again they are only distantly related to the core of what metal is in the first place. -