Gates was born in Bradford to father Paul Gates and mother Wendy Broadbent. He joined Bradford Cathedral choir at age nine. He was head chorister at Bradford Cathedral by the age of eleven, singing solo for the Queen when she visited in 1997. Gates achieved Grade VIII in piano, classical guitar and singing. He had gained a place at the Royal Northern College of Music before the finals of Pop Idol.

Gates was runner-up on the first series of Pop Idol in February 2002. Despite not winning the competition, he was soon signed up with Simon Cowell's record label BMG.

Gates' first single, a cover version of "Unchained Melody", entered the UK Singles Chart at number one. The single went double-platinum in the UK, and was voted 2002's Record of the Year by ITV viewers. This was followed by another number-one single, "Anyone of Us (Stupid Mistake)". His third single, "The Long and Winding Road", a duet with Will Young, also reached number one. His fourth, "What My Heart Wants to Say" reached number five.

His debut album, What My Heart Wants to Say achieved first week sales of over ten thousand and double platinum status. It was the third biggest-selling album by a UK artist that year.

In 2003, Gates sang the 2003 Comic Relief charity single, "Spirit in the Sky", with The Kumars. This was a number-one hit for two weeks. He also appeared in Comic Relief's Celebrity Driving School. Through Comic Relief, he became involved with Body and Soul, a charity that helps people affected by HIV and AIDS.

His next two singles "Sunshine" and "Say It Isn't So" reached numbers three and four respectively. His second album Go Your Own Way peaked at number eleven in the UK. It charted at number 1 and achieved platinum status in a number of Asian countries. Gates won MTV Asia's award for Best International Male in 2003/4 and was awarded the same title by MTV China and MTV Taiwan.

Gates has sold just over three million music singles in the UK, including the second and sixth best selling singles in 2002 ("Unchained Melody", which sold 1.3 million, and "Anyone of Us (Stupid Mistake)", which sold 570,000) and the second best selling single in 2003 ("Spirit in the Sky", 550,000 copies).