''The best thing about Rob is that he is a really great actor,'' says Pearce.
''Watching the rushes back, you go: 'OK, he is just going to be fantastic'.''
''He plays (the character) slightly backward, emotionally useless and really vulnerable,'' says Pearce.
''He's got this beautiful face so you are completely entranced by that face no matter how ugly he makes himself or how wounded he is, or how manky his haircut.''
OUCH.. but we're kind of loving it! - Pearce also shared more on the film while he promoted Iron Man 3 on TV. (at 3:25).
(CLICK TO WATCH - comments @ about 5:20)
At about 1:00
Guy Pearce has given a glimpse of what to expect from The Rover, the futuristic film he finished shooting with Robert Pattinson in outback South Australia last month.
Director David Michod's keenly-anticipated follow-up to Animal Kingdom is "an unusual story" set in a world gone wrong in the near future.
"It's a military state now, it's every man for himself a little bit, it's a very bleak kind of world," says Pearce, who's about to reach cinemas as the villain in Iron Man 3.
In The Rover, the Australian star plays the title role, a damaged man named Eric with nothing left to live for. Trying to track down a dangerous gang, he meets a young stranger, Rey (Pattinson), and they forge an uneasy alliance.
"[He's] somebody he has no interest in," Pearce says. "He's purely using him to get where he needs to go. So through this bleak ... world, there's a little connection that's kind of made, which on some level you might think would be a positive thing for this character.
"But on some level it actually makes things worse for him - to really believe that there's some sense of love in the world or any sense of humanity or compassion. So it's a pretty bleak story."
As filming finished in the small town of Marree, almost 700 kilometres north of Adelaide, Pattinson said he wanted to be part of The Rover because "it was a startlingly original script, and it was one of those parts where you read it and you think, 'I'd love to do this, but I know I'm never going to get it'."
To play Rey, the Twilight star was dressed as unkempt and unshaven, with make-up to discolour his teeth.
Pattinson says his character, an American who has come to Australia with his brother (played by Scoot McNairy), is "the kind of person who has been brought up to believe they're incapable of living independently. Someone has always been looking after him."
The two central characters, Eric and Rey, have a shifting relationship that Pattinson described as "strange and disturbing."
It's a film, expected to be out later this year, that seems to have echoes of the classic post-apocalyptic Australian film Mad Max.
''Not as camp though,'' says Pearce, was also in Animal Kingdom. ''Mad Max is great, don't get me wrong. But it's heightened in a way, whereas this is pretty earnest.''