If you dream of singing, it can mean you have expressions which you had kept under wrap. It is time for your soul to release these pent up emotions.
If you dreamed that you were singing a joyful song, it means you were happy during that day.
If you dreamed of yourself singing a sad song, it can mean you had troubling thoughts during that day.
On the whole, dreaming of singing is a good dream metaphor. Your inner psyche has expressed its need to release communication about itself.