Michael Fassbender has made a confession that will cause couch potatoes everywhere to rejoice - he hates the gym.

The Irish actor walked the red carpet in Sydney for the premiere of the upcoming X-Men: Apocalypse film in which he returns as the powerful Magneto, and admitted he is no gym bunny.

"I find the gym one of the most depressing places in the world, if I'm being honest," Fassbender said.

It's hard to believe that the man who made his big break playing a muscle-bound Spartan in the 2006 film 300 doesn't bench-press weights during his down time.


But Fassbender, who is in Sydney filming Ridley Scott's sequel to 2012's Prometheus, Alien: Covenant, finds other ways to stay in shape while in Sydney.

"I do like being active and playing games," he said. "So at the moment I'm enjoying learning to surf ... I've been learning for a while, I don't think I'll ever stop learning. I was one of the ones who picked it up late so I think I'll always be somebody that started surfing after the age of 35."

The Oscar-nominated actor isn't just focused on his physical side. In his third outing as Erik Lehnsherr, aka Magneto in the X-Men series, he's enjoyed getting into the complexities of what, at times, can be a very dark character.

"He's a complicated guy and there are layers to him. His history is so violent and there's so much there in terms of something to mine from as an actor, it makes it a lot easier. And the sophistication of his relationship with Charles [Xavier - played by James McAvoy], all those things really I find very endearing about the character to play him," he said.

Having known his fellow cast mates including McAvoy, Jennifer Lawrence and Rose Byrne since 2011's X-Men: First Class, Fassbender says they've developed a close bond.

"It's like family, really, that whole First Class group of us."

Some new faces have joined the cast as we learn the back story to some of the popular characters, including Game of Thrones actress Sophie Turner as a young Jean Grey and Kodi Smit-McPhee who plays Nightcrawler.

"We're introducing new family members, a new generation in this film, so that's going to be fun for the fans too," he said. Fassbender has quite a few fantasy films in the offing including X-Men - there's also the upcoming video game adaptation Assassin's Creed.

"I'm a fantasist," he said, with a smile.

Although, he says, working with a blue or green screen is really just like doing theatre.

"It's the same approach, really, you're just imagining things that aren't there. They'll fill them in later, of course."

While he admits he's soaking up everything that Ridley Scott has to teach him on the Alien: Covenant set in Sydney, he will be promoting some very different films soon.

In September he releases The Light Between Oceans, where he met his current partner, Oscar-winning actress Alicia Vikander, and Trespass Against Us, a movie about the travelling community in the UK.