They are not Christian, like BrotherReed pointed out. In fact, one of my friends told me that the "Green" in Green Day actually means marijuana (my friend is a Green Day fan). So, in essence Green Day means Marijuana Day! Anyways, I do like a few of Green Day's songs (like Boulevard of Broken Dreams and Holiday), but the problem I have with them in general is that they swear a lot and sing a lot about negative things like drugs. I don't think that songs like Boulevard of Broken Dreams are that bad to listen too (besides the fact that it says "the f-word" in it once) because it does not sing about bad things, but most Green Day songs do. They are not the best band to listen to (becuase of lyrical content/bad language), but they are alright as long as your careful about which song of theirs that you listen too.