A metal taste in the mouth can be caused by several different medical conditions and things such as, Hormonal changes, medications, Respiratory Infections, Hepatitis B, Acid Reflux, Oral Thrush, Dry Mouth and even poor hygiene of your mouth.
Gum and Tooth problems such as gingivitis, periodontitis and tooth infections can also cause metal taste in the mouth.
Diabetes and even low iron can cause you to have a metal or metallic taste in your mouth so if you continue to have a metal taste in your mouth that doesn't go away then you should see a doctor about the problem to make sure you're not having other medical conditions that can be treated.