Everything about Sam Worthington exudes rugged masculinity, from his favourite worn-in Blundstone boots and generic-label jeans to his furrowed brow and stubbled jaw. Critics may be quick to brand the 32-year-old actor gruff, but Academy Award-winning director James Cameron prefers "old-school tough guy" - the very reason he cast the one-time bricklayer as the star of his $US200 million sci-fi epic Avatar, due out in December.

Worthington is either a genuinely tough bloke, or he's pocketing a motza for doing a brilliant impression of one, playing cyborg Marcus Wright in Terminator Salvation (opening on June 4), the fourth instalment of the blockbuster franchise. "Sam had me at 'Uh huh,'" Cameron said at the Australians in Film event in Los Angeles. And despite only having viewed the Terminator Salvation trailer, Cameron predicts the Perth-born actor - he recommended him to director Joseph "McG" Nichol - will blow his Hollywood co-star Christian Bale "off the screen."

It's a big call for a bloke who, at age 19, decided to audition for the National Institute of Dramatic Art (NIDA) just to keep his then-girlfriend company. "I had dreadlocks and I thought [playwright] Chekhov was on the starship Enterprise," Worthington tells WHO. "In hindsight, I was a sponge. That bravery gets you far, and then it gets knocked out of you and you start doubting things. You need to surround yourself with people who make you stronger."

Nowdays, that role is often played by Titanic director Cameron: "Jimmy's Jimmy - I could go on and on about him because he's changed my life," says Worthington. But back in his formative teenage years in the West Australian coastal town of Rockingham, the keen surfer's mentor was his father, powerplant worker Ron. "I've always been strong because my dad would kick it into me," says Worthington. "'Stand up for yourself,' he'd say. 'You only get one shot in this life, and you don't want to make a mess of it.'" While Worthington's parents think it's "damn funny" that they can "throw friggin' Jaffas at my head in the cinema," the impact of his dad's advice couldn't have resonated more seriously with the self-described "gypsy."

Leaving home to travel around Australia at age 17, the tradie became an actor "by accident" after he was accepted into NIDA, his then-girlfriend overlooked. After graduating in 1998 ("Every day I thought they were going to kick me out"), Worthington immediately won a starring role in the acclaimed movie Bootmen, followed by parts in Dirty Deeds (2002) and Getting Square (2003). But after promoting his boyish charms the following year to play farmer's son Joe in director Cate Shortland's AFI-winning film Somersault ("He just came in and had this fantastic sense of danger and honesty," recalls Shortland), Worthington began shuffling towards the big time - a move boosted when he joined the cast of the Foxtel success story Love My Way in 2005.

The risk-taker's keen pursuit of the action was obvious on the Terminator set, where he injured himself "every day" performing his own stunts. "On this scale, where you've got more money being thrown at you and more responsibilities, if I don't give 100 per cent, then what the hell am I doing?" he reasons. It's a level of commitment that has seen Worthington snapped up to star in back-to-back feature films over the past 18 months: he just wrapped Last Night, opposite Keira Knightley and Eva Mendes, and is now filming a remake of the Greek-mythology epic Clash of the Titans with Liam Neeson and Ralph Fiennes in the Canary Islands.

Still, the bloke who says life away from work is simply to "hang out with my mates, do my washing and get my balls busted by my girl" (Sydney stylist Natalie Mark) is quick to quell the hype. "I'm just a guy with two bags and no base who travels where the work is," he says. "I'm still an infant, I'm still learning."

By Sarah Grant