I want to get some more detail information about your problem,
How long the problem is there ?
Do you have tooth problem / sinus / acidity or any other disease?
Do you take any other medicine?
Waiting for your reply.
The metallic taste or impaired taste is known as Dysgeusia.
The causes of metallic taste in the mouth are
Sinus or nose, tooth infection, flu, common cold, dry mouth
Heart burn, reflux
Any continued exposure to any metal like selenium, mercury, lead, copper etc.
Some drugs like metronidazile or many others also can cause metallic taste in mouth.
You can read for more information in the Link.
If you do not feel any predisposing factor, then you should be checked by doctor to examine you to find out the cause.
I hope this information will help. Please press the ACCEPT button if I answered your question. Thank you.