Are your gums bleeding? I get a mineral taste from the numerous meds I take, but usually if I have a metallic taste, its blood. Orrrrrrrrrr....by chance do you keep your breathe mints or gum in the same place as your spare change? Just a thought....sometimes it's the most obvious answer...good luck finding out what's up!
Have you recently ingested any zinc cold remedies? These products can cause olfactory nerve damage which results in odd smells/tastes and even a complete loss thereof. I have olfactory nerve damage from a zinc cold remedy (cough lozenges) and I smell sulphur or burnt hair all the time. When the damage first occured I smelled ammonia very strongly.