MGMT performed "Your Life is a Lie" from their upcoming self-titled album, which is slated for release September 17th.
This might be the first time anyone has ever written this sentence, but I think they need to dial it back with the cowbell a little bit. Somebody might want to tell these guys that the famed cowbell sketch with Christopher Walken and Will Ferrell was not a documentary. The audience on Letterman seemed underwhelmed, if they were whelmed at all, but perhaps the demographic that attends a Letterman taping isn't ready for comically over-sized percussion and star-shaped glasses.
Watch the video above and you can pre-order MGMT via iTunes.