The 48-year-old is set to play the frontman of an 80s glam rock band in the new movie version of Broadway musical Rock Of Ages.
And the film's director is impressed with how hard he has been working for the role.
According to website The Wrap, director Adam Shankman said: 'He's been studying with - seriously - Axl Rose's voice teacher like five hours a day.
'The prognosis is more than excellent.'
He added: 'I think we're going to see him, every drop, the rock 'n' roll God!
'I'm very excited. He's so committed to doing it.
'He's pouring himself in this part in a way I've never had an actor do. It's pretty intense.
'Between the voice lessons, the incredible study - researching the period, it's like 1987, just going there!'
Other stars set to feature in the film are Alec Baldwin and Russell Brand.