The crowd sing along with a lot of LP songs. BIO, BTH, ITE, APFMH, LFY to name just a few. Its certain sections of the song and its encouraged by the band. It feels just the right amount of crowd participation to band performance IMO.
However, what 30STM do is really poor in comparison. I'm sure 30STM don't see it that way and think its awesome. Likewise for their diehard fans singing their hearts out. For me, as a casual fan of 30STM, I like their studio stuff but they're really poor live.Even when Leto does sing, he barely sings a full line or chorus because he's so out of breath from running all over stage.In comparison, Chester moves around a lot, dances, jumps etc but is still able to give a damn good live performance and doesn't skip words, sing unfinished lyrics due to be out of breath.