My tongue has a white coating and I have a metallic taste at the front of my mouth. I've tried cleaning it with my tooth brush, but it comes back, also it is really far down my tongue where I can't reach. What do I do?

Dentist consult. See a dentist for a complete and thorough medical and dental history and a one on one clinical exam.
Trench Mouth. Good day;
Usually these symptoms, especially the metallic taste are symptoms of Acute Tecrotizing Ulcerative Gingivitis; usually gums are are tender, bleed and painful. Considered a noncontagious infection of the mouth. Found in students around exam time or soldiers before battle. Consider a dental visit in the near future.