Help with recording voice over a track?

okay, i make beats for fun. kids in my school wanna rap over them now. i tried it out on my friend and it just sounds bad. im using sony acid 7. i feel like its not blending with the music, it just sounds like some guy rapping over it, you know? Im not using a recording mic, but is there a vst out there that can help me? all help is appreciated.!