Here's a 2015 video of the late soul singer, Charles Bradley, covering Black Sabbath's "Changes," from their 1972 album, Vol. 4. While it may seem a little unusual for a soul singer to be covering Sabbath, "Changes" has always struck me as basically a soul ballad.
If you go back and listen to the original and compare it with the Bradley cover, you'll see that, minus his deeply emotional delivery and James Brown-like soul screams, he's actually quit faithful to Ozzy's original vocal. The song, written by Geezer Butler, is allegedly about the break-up of drummer Bill Ward and his first wife.
Here is a touching duet version of the song that Ozzy and Kelly Osbourne recorded in 2003. As one YouTuber commented on the song, "This is where metalheads go to cry."