I have a metalic taste in my mouth when i cough. what might be the cause.?

URI, cold, bronchial: Change in quantity and type of mucus in response to a bronchial infection can taste different in your mouth when coughed up. Resolution of the cold, bronchitis etc., should return things back to normal, no apparent taste. Regular mucus probably has some minimal taste but you just get used to it and don't notice it. You're noticing the change.

Dydgeusia: can be a sign of infection or hormonal change. See your doctor.