If you grew up listening to metal or had older brothers and sisters who did, you probably heard DIO, saw a DIO shirt or maybe even went to his concerts. You most definitely threw up the devil horns and you probably heard this Black Sabbath album at some point:
In 1979, after leaving Rainbow Dio replaced Ozzy in Black Sabbath. They released "Heaven and Hell" which totally changed the sound and direction of the band. Not to mention that it was a commercial success. Dio left to form his own band in 1982 and most recently was working on a project with Iommi, Geezer and Vinny Appice called Heaven & Hell since all four played and toured together during Dio's Black Sabbath era.
Dio died of Stomach Cancer May 16th, 2010. And despite having a huge influence on metal; barely any word in the media about his passing. You can leave condolences and messages on his Facebook page.
RIP.