Why am i having this metallic taste on roof of mouth?

Common occurance: Metallic taste in your mouth is quite common and usually is nothing to be concerned with. It can be caused by medications such as some antibiotics, high blood pressure medications, antidepressants and some vitamins. Other causes are infections, such as an abcessed tooth, gum disease and poor oral hygiene. Many time the cause can't be found. This usually will go away but this can take some time.

Leaking filling: You could have an old dental amalgam filling which is leaking and the taste could be perceived as metallic.