Melanie is a 44-year-old mum-of-two, who works as a music teacher for under-5s. She reveals that music "is the only thing [she's] ever wanted to do", but she believes that the ITV1 talent show is her last chance of getting a big break.
Her audition is believed to be part of the reason that Gary Barlow has backed the Overs category as the "one to watch" in series nine.
Speaking after her performance, the Take That star says: "Melanie that was insane. Oh my god, that voice! You were guiding us through the song. It was amazing, it really was."
Louis Walsh comments: "Melanie, where did that voice come from and where has it been? You're 44, this is what this show is all about - finding somebody as amazing as you and giving them a chance."
Guest judge Anastacia says: "I completely can't believe that you killed it like that. It is never too late to have a record deal girl!"
Tulisa Contostavlos concludes: "You came on stage and you seemed really gentle and then all of a sudden this fire and this soul and this diva came out of you. You owned that stage, you absolutely rocked it - that is how you do an audition. Amazing."
Meanwhile, on this evening's Xtra Factor, Melanie takes Olly Murs to her music class. The pair dress up as Fairy Flutterby and Olly Murs Flutterby and the popstar dons some pink wings to work with her for a day.
The X Factor airs tonight (September 1) on ITV1. The Xtra Factor follows afterwards on ITV2.
X Factor Show 3 - Photo gallery:
Copyright: ITV Thames TV/Ken McKay