I would say melody, not beat, but lyrics are still really important too. The only reason I go with the music is I like some shoegazey music where there are vocals that are unintelligible, and I like some instrumental music.
My favorite song is Imagine by John Lennon.
The lyrics are by far the most intriguing part of the song, but it really does go hand-in-hand with the music.
So both, really (with a slight emphasis on the poetic aspects).
Don't care that much about the lyrics as long as they're not socialist or religious.
The important part is that the video that comes along with it has a cute girl in it - preferably wearing very little.:tongue: