"Light On" is the first official single released from American Idol season 7 winner David Cook's major label debut studio album, David Cook (2008). It was released through RCA Records on September 30, 2008. The song reached No. 17 on the Billboard Hot 100 and was certified Platinum by the RIAA.

"Light On" was co-written by Soundgarden and Audioslave front man Chris Cornell, as well as producer/songwriter Brian Howes. The song was produced by Grammy-winning producer Rob Cavallo, who has produced hits for Green Day and Kid Rock. The song also displays Cook's upper register, with the singer hitting a high C at the end of each verse.

The song's lyrics were posted on Cook's official website on September 22, 2008. "Light On" officially debuted on AOL Music's PopEater section on September 23, 2008. It became available for radio airplay later the same day, but officially went for adds on Mainstream Top 40, AC, and Rock radio on October 13, 2008. It was released via iTunes and Amazon on September 30, 2008.

Reception of "Light On" was generally positive to mixed. Billboard's Chuck Taylor said that "melodically, there's no question that this bullet is heading right for the brain, where the only thing stickier than the chorus is Cook's appreciably sweaty performance". He predicted success for Cook, stating "Like Chris Daughtry before him, here's an Idol who is bound for true rock cred", summing it up with "Light On" is right on."

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