Sorry. Seriously, no, a song doesn't need a bridge. But the purpose of a bridge is mainly to avoid boredom...it usually hits after a couple of verses and choruses and gives us something different to chew on. They can also be the place where some sort of major change happens in the lyrics. It can be really short or as long as a verse...but on the other side of that bridge, we come back to a verse or chorus again.

Sometimes they're only just a line, phrased slightly different than the other elements of the song. Sometimes they are an entirely new section.

So, no, songs don't NEED bridges. But it's always good to put on your "BoredoMeter", that part of you that can objectively determine whether or not your song is becoming monotonous, and decide whether a bridge will benefit your song.

I LOVE bridges. I really like when they drift off into strange places...it seems the stranger I can write them, the more effective it sounds when it comes back into the main theme.

http://www.soundclick.com/MarkKaufman