Is Iron Maiden the biggest metal band in the world right now?

Ozzy has lots of Hard Rock and Ballads but he also has some classic Heavy Metal songs.
Plus he was part of Black Sabbath that is considered the first Heavy Metal band and so he has always been seen as a Heavy Metal figure.

The market in which they circulate are also important and Ozzy has always circulated in the Heavy Metal market whereas Deep Purple, Van Halen, AC/DC, etc have always circulated in the Hard Rock market.

I've known lots of people who claim to not like Heavy Metal at all who are surprised when I show them some Ballads and Hard Rock songs by Ozzy Osbourne because they had this prejudice about him.
This clearly shows that even if his music is not 100% Metal he has always circulated inside the Metal market.

Black Bart

Ancient Mariner
I should have been clearer: I was taking of Ozzy's solo output (excluding Speak of the Devil obviously), not Black Sabbath. ;)
Some of his songs like Crazy Train, Over the Mountain, Bark at the Moon, etc are on the edge between Hard Rock and Heavy Metal.
They could be considered Heavy Metal I think.

Some others definetely are Hard Rock and many are Power Ballads.