I need help with picking a slow soulful rnb modern song to sing at my highschool band concert!!!?

OMG!! i am soooo nervous because i'm performing infront of the ENTIRE school next friday with my band cl, i'm not nervous about performing just choosing the right song. Anyway i'm going to be sitting on a stool for this performance so i would like to sing a slow soulful powerful song that is modernish and majority people would know it. Any ideas. I like songs like Halo-beyonce, If this isnt love-Jennifer hudson, and etc. Thanks guys and let me know what your opinions are please! :D