Not knowing is fine. Everyone has to find everything out for the first time.
The point I think is knowing, or at least being able to assess, what everyone else might know. Chances are, on a metal website, Rob "metal god" Halford having sung for THE metal band Black Sabbath is bound to be common knowledge.
27/4 Dan Patlansky
3/5 Maiden United
7/5 One Machine
8/5 Blaze Bayley