Rage Against The Machine rocker Tom Morello has teased that some "huge superstars" could make a surprise appearance at the last ever Black Sabbath concert.

The 60-year-old guitarist is the musical director of the 'Back to the Beginning' show which will take place at Villa Park - the stadium of Premier League football club Aston Villa - in Birmingham, England, on July 5 and it will be the final time Black Sabbath's original line-up, Tony Iommi, Geezer Butler, Bill Ward and Ozzy Osbourne, will perform together.

The line-up also includes Metallica, Slayer, Pantera, Gojira, Alice In Chains, Halestorm, Lamb Of God, Anthrax and Mastodon, as well as supergroup of musicians also playing, including Billy Corgan, David Draiman, Duff McKagan, Frank Bello, Fred Durst, Jonathan Davis, Scott Ian, Sleep Token's II and more.

Morello has now teased that fans in attendance could see some other metal legends take to the stage on the day.

Speaking to Australian Musician magazine, Morello said: "Where it's at now… First of all, when we first sat down, we have a very, very simple goal, and that's to make this the greatest day in the history of heavy metal.

"And to that end, you've probably seen the listed setlist. And let me tell you, there's some huge superstars who are gonna be surprises on that day too. So, the idea is to really acknowledge the importance of that band in a way that the whole world will forever know it."

Morello also revealed he got the musical director job because 76-year-old Ozzy - who is living with Parkinson's disease and the lung condition emphysema - and his wife Sharon Osbourne, 72, personally asked him.

He said: "It came about [because] Ozzy and Sharon asked me to do -- they surprised me one day and said, 'There's gonna be one more Black Sabbath show, all four original members, the last-ever Ozzy Osbourne show. We wanna have a big day of celebration and will you help curate it?' And I was, like, 'Well, that's crazy. But yes, of course.'"

Previously speaking about the job being an honour on Chicago radio station WBEZ, Morello said: "Heavy metal is the music that made me love music, and Black Sabbath is the band that invented heavy metal. So, when Ozzy and Sharon Osbourne asked me to be the musical director of what's going to be the last Black Sabbath show -- the last Ozzy Osbourne show in the soccer stadium that's like a half-block down from where Ozzy Osbourne and Geezer Butler, the bass player of Black Sabbath, grew up -- I was honoured to do that."