It could also be an abnormal perception of bitter taste
called dysgeusia. GERD and heart
burn too cause metallic taste
in mouth. Post nasal drip as in sinusitis, salivary glands infection, pharyngitis or strep infection too are common causes. Certain dentures and artificial tooth or filling of dental cavities too give a metallic taste. Sjogren’s syndrome and copper or lead toxicity are other possibilities.
I think you should discuss these possibilities with your doctor.