Adam Lambert joined X Factor finalist Saara Aalto in the traditional X Factor duet today (December 10).

Aalto started singing 'Bohemian Rhapsody' alone playing a grand piano when Lambert walked on stage and onto the top of the piano. The duo delivered a stunning and flawless performance of the Queen classic. Their version helped secure Aalto's place in the X Factor Grand Final top two.

The X Factor contestant's first song of the night was a slowed down version of Tears For Fears' 'Everybody Wants to Rule The World,' which would compliment Lambert's haunting version of Tears For Fears' 'Mad World', a song he performed on 'American Idol'.

A week ago Aalto revealed that she would love to duet with Lambert if she made it to the show's finals. She said: 

"I have so many choices... maybe Adam Lambert because he’s so theatrical and we could do a big number together."

When asked by show host, Dermot O'Leary about Aalto, Lambert said:

"Saara is a superstar, ladies and gentlemen!"

He then spoke in Finnish to her, and she replied in her native tongue.

Lambert's ex-boyfriend was also Finnish, Sauli Koskinen. 

Aalto said: "I've wanted to perform with Adam for ages, and the X Factor made my dream come true!"

Both Aalto and Lambert are gay and both Freddie Mercury's biographer and Sir Tim Rice, the acclaimed lyricist, revealed last year that 'Bohemian Rhapsody' contains a hidden message about Mercury coming to terms with his own sexuality.

The winner of this year's X Factor will be revealed tomorrow (December 11). The two finalists are Matt Terry and Saara Aalto.

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Watch Adam Lambert perform 'Mad World', Saara Aalto sing 'Everybody Wants to Rule The World' and their duet below