Thrashtilldeth wroteAdveser wroteThe real answer is whatever is the closest to what Dio was doing.
Adveser, old boy, I'd totally misjudged you. You're alright.
Dio created metal as far s I'm concerned. I think the maiden/priest being the real start of 100% metal is correct. Except that dio was really doing all that same sort of thing since he started Rainbow with Blackmore. Yeah, I'll get some shit for not crediting Sabbath, but then you have to include BOC and a thousand other bands that were not really bonafide 100% metal with absolutely no hard rock pretensions or asperations for pop/rock success.
Dio created metal's style of singing end-of-story for me, even using tamed down versions of the harsher styles and overblown operatic styles at the opposite end, though he wouldn't take it in the Bel Canto directions some others would like Tate...