Regular Pop music, Rap, and even Country often have themes or subjects that conflict with Christian values. It is difficult to stay connected with God when your iPod fills your ears with songs celebrating adultery, "getting wasted", materialism, and other activities incompatible with the Christian lifestyle.
One of my favorites, "Victor's Crown" by Darlene Zschech is particularly beautiful. (You owe it to yourself to listen to this song with a good pair of headphones, turned way up. Goosebumps.)
If your idea of "worship songs" is rooted in a dusty hymnal written in 1852, you owe it to yourself to tune into one of the above sources and sample how exciting modern Christian music can be.
(FYI: You're free to dance.)
