Hugh Jackman is ''very hard to calm down'', according to Zac Efron.

The 30-year-old Hollywood hunk - who appears alongside the 'X-Men' star in the new movie musical 'The Greatest Showman' - says his co-star is as ''perfect as it gets''.

Speaking to news.com.au, Efron said: ''When he sings, if he wants to hold a note, if it's like 'Today...' he'll naturally sing, 'TODAAAAAAAAAAAY'.

''He has this natural vibrato that's very hard to calm down. He admits it's hard to calm down from years of being on Broadway.

''Other than that, he's as perfect as it gets.''

The new movie - which is helmed by Michael Gracey - follows the true story of P.T. Barnum, an American showman, politician, and businessman remembered for promoting celebrated hoaxes and for founding the Barnum & Bailey Circus.

Efron and Jackman appear alongside 'Spider-Man: Homecoming' star Zendaya in the movie.

And the 21-year-old actress has hailed Jackman's positive approach to life.

She said: ''He's very terrible at being a negative person, he just can't do it.

''I don't think there's a negative bone in his body.''

Meanwhile, Jackman - who stars as the ring master in the film - recently revealed he went against doctor's orders to sing at his audition, just a day after he underwent a skin cancer operation on his nose.

He said: ''I thought there's about a one in 10 chance this movie happens. But we're going for it. My doctor had said, 'Do not sing, you've just had 80 stitches in your nose. They really could split apart, you could get an infection', which I'd had before in a similar operation.

''So I was like, 'Don't worry I'm not going to risk that, I'm just going to speak it and someone else will sing it.' But the emotion of the song and the moment took over me.''