"Thunder" is a song by British singer and songwriter Leona Lewis from her fifth studio album, I Am (2015). The song was written by Lewis and Toby Gad, who also produced the track. Lyrically, "Thunder" is about finding the strength to pick yourself up after falling on difficult times. Lewis explained that the song is about self-reflection and self-empowerment and finding the ability to look within in order to decide what is best to do next. Def Jam released "Thunder" on 24 July 2015 as the lead single in United States, but it is the third single to be released from the album overall. Remixes by Danny Verde and Tom Swoon were also released.