The 10-year-old Canberra schoolboy got his rock god on and performed on a stage emblazoned by real flames in the grand final on Sunday night.

It's now down to the public vote to decide the winner of the $250,000 first prize.

Callum performed Through the Fire and Flames by DragonForce.

"They say it's the hardest song to play on Guitar Hero and that you should just actually learn guitar instead," his dad Doug said, on Sunday night.

"It takes two of the top fastest metal players in the world and a singer to perform what Callum tackled himself."

The judges, particularly Kelly Osbourne, were full of praise for his performance.

"Callum, you are such a rare breed of human being....You are born a rock star and I'm just so proud of you," she said.

Ian "Dicko" Dickson said he was amazed how far Callum had grown during the show.

"That was genius mate, fantastic," he said.

Another judge, Eddie Perfect, said "I think you can do anything you turn your mind to ... I think you're an unstoppable force".

The super-smart 10-year-old was fast-tracked to start high school this year and wants to be an astrophysicist as well as a musician.

So, naturally, he had to apply some maths to the music.

"There are 11 people in the grand final, 10,000 people auditioned, there was almost no chance I'd get here!" he said, on the show.

"It's a 0.11 per cent and I'm just so happy that against all odds I've made it here."

The pint-sized rock star has said should he win the $250,000, he wants to donate some to charity, put some into his music and education - and to buy a new cat for his family after the 22-year-old family moggie passed away recently.

To vote for Callum, ring 1902 559 002 or text Callum to 1970 22 99. Lines close at 6.30pm on Monday.