Hi,
By what you are describing you seem to be having Bell's palsy. This is the palsy of the seventh nerve. The metallic taste in mouth is also due to that. Nerve palsies are seen commonly in Diabetics. You need to have your blood sugar levels controlled. No need to worry this recovers on its own in a few weeks. You will need to fix an appointment with your daibetologist. for more information read here... and here...
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regards
Dr. Gupta