What does it mean if i have a slight metallic/sour/acidic taste in mouth? i doubt its an dental issue because i brush my teeth well (braces)..

Hard to tell: Sour/acidic taste may be normal. I get a lot of it depending on what i eat. Metallic taste? - braces? Occasionally, acid reflex from the stomach may be the culprit, but less likely.

Possibly reflux: It is possible acid may be the cause. If you drink or eat a lot of acids (coffee, tea, sodas, tomatoes, oj, etc) it can irritate your mouth and possibly lead to reflux where stomach juice can come back up often without you being aware of it. Try a liquid antacid after you eat and before bed. If it doesn't improve quickly see your dentist to make sure all is right with you braces and then ent.

Many causes: Can be from leaking filling, broken tooth, coppery taste from bleeding (infected) gums, acid reflux, infected tonsils/adenoids, medications, failure to clean between teeth where toothbrush can't reach, etc. Start with your general dentist and your orthodontic specialist. Have them check for oral cavity issues. Go on from there to your general physician. I'm sure there's a logical explanation.