Why do i have a metal taste in my mouth ?

I don't know, and without more information it is pretty much impossible to tell. However, you have noticed a change, so what could have caused it. Different food, a change of medication, a different brand of toothpaste, a dry mouth or a cracked filling or restoration. Brush floss and rinse, nightly, give it a few days and if it persists ask your doctor.

This is called dysgeusia and is caused mostly from food allergy. Broken or loose metal fillings in mouth can cause this taste. Also the taste from metal dentures is a possibility. If this taste continues a long time than there could be some underlying medical problems which should be addressed.