What Causes Bad Breath, Bitter Taste In The Mouth And Dry Mouth?
You may need to meet a dentist
There can be two main causes for the bad smell and metallic taste which you are experiencing
The first and most likely cause may be an infection of the teeth or gums. Mouth rinses will be effective only in early infections and therefore you must meet a dentist and get your teeth checked
The second reason may be a sinus infection, which may also cause the black sputum and bad smell. You can start steam inhalation thrice a day and meet an ent doctor for further evaluation
Hope I have answered your query satisfactorily