Hi.. Can understand your concern.. As per your complain burning sensation of mouth with a metallic taste can occur due to Burning Mouth Syndrome and as you are taking Gabapentin the dry mouth can be due to side effect of the medicine.. The dryness of mouth can lead to atrophy and burning of mucous membranes along with altered taste in mouth as the saliva is required for proper flushing action and proper working of taste buds.. I would suggest you to consult your physician and explain him the current symptoms so that he can either reduce the dose of medicine or change the medicine if possible.. For the dry mouth and burning sensation you can use saliva stimulators like sour candies or sugar free chewing gums which can trigger the salivary glands and increase flow of saliva.. Saliva substitues can also be taken to lubricate the mouth . As the lubrication will increase the burning and altered taste will reduce.. Maintain better oral hygeine. Gargle using on alcoholic mouthwashes.. Hope this information helps.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.