Lead vocalist Alex Gaskarth stated in an interview with MTVu that "The whole mentality of the song is like, you feel like you're stuck in this like, negative space and you just want to get out. Summer's rolling up and uh, everybody's finishing up with school and everybody's getting like the exam beatdown".
In the Nothing Personal album trailer, Jack Barakat said that the song is about not wanting to grow up and just wanting to be a kid.
The music video for "Weightless" commenced filming on May 20, directed by Matthew Stawski. Fans were invited to go on the set and be a part of the music video. It debuted on MTV, MTV2, mtvU and HITS the day before the album's release, on July 6, 2009. The video features cameo appearances by Pete Wentz from Fall Out Boy and Mark Hoppus from Blink-182 with a joke that Pete Wentz tweets (on mobile Twitter) that All Time Low rips off Fall Out Boy, but Mark Hoppus thinks to himself that both All Time Low and Fall Out Boy rip off Blink-182. The camera follows the action through the venue, with text that is insulting everyone, stating "Loser!". The video ends with the slogan Nothing Personal, which is not only a reference to the album, but is also the theme of the video.