An astrological symbol depending very much on the circumstances and other symbols in the dream.
The Sun is the giver of life, and therefore dreaming of a bright Sun high in the sky is an omen that you will soon be able to live the kind of life you want.
A Sun obscured by clouds implies that your current prospects are uncertain right now, and you may need to reevaluate your situation and make some adjustments.
The rising Sun represents beginnings and the setting Sun endings. Whether the beginnings or endings are positive depends on the circumstances (especially the weather) and the other symbols in the dream.