Burning sensation as well as metallic taste
in mouth may be due to impacted wisdom teeth which is inflamed.
I would advice you to visit a dentist
and get the wisdom teeth extracted or saved.
Decayed teeth if present,has to be extracted or restored.
Use warm saline rinse to gargle.
Rinse your mouth after every meals.
Use desensitizing toothpaste and soft bristled toothbrush to clean your teeth.
Maintain oral hygiene
Hope this helps.