One of the very common cause of metallic taste and dry cough is gastroesophageal reflux disease (GERD). So that needs to be ruled out. Despite that you are a social smoker, it helps in the problem, if smoking is quit.
Read the resource, which tells you about the detailed causes and what to do for the metallic taste;
Gum, teeth infections, oral cavity inflammation and medications are the other common causes for the metallic taste.
Seems to be not a big concern.
Please feel free for your follow up questions.