Hello , Thanls for consulting hcm Read your query as you have burning sensation on tongue , metallic taste , dry mouth this can be due to some reason with include drug induced , vitamin deficiency, malnutrition , allergic reaction , respiratory tract infection or liver disease . For this I will suggest you to consult oral surgeon and good physcian for examination of oral cavity and complete blood chemistry to evaluate the cause . Inmeantime do warm saline rinses and maintain good oral hygiene and use chlorhexidine mouthwash regularly . Hope this will help you .