Some of you that used to ferment in plastic or glass run into a batch that has a "metallic" or "tinny" flavor to it and sometimes ask us "is it the metal that makes that flavor?"
No - this is most likely from your yeast. (Assuming, of course, you have properly cleaned your unit per our instructions using TSP, Starsan, etc.)
Some metallic tastes are possible during stages of the fermentation, there's a lot of chemistry happening. There are also possibilities of the yeast itself creating the metallic taste.
Yeast which is under stress or not healthy to start with will create a metallic taste that remains with the beer it is part of the yeast expelling minerals as part of its natural defense. You can read all about this in Chris White's Yeast book.
Was this the first time using that type of yeast? Was it harvested from a prior batch? Was it old, near its expiration? Was it stored well, both at the store and after you purchased it? Was the pitch temperature correct? Did the temps swing up/down during fermentation? Did the wort have proper PH? Did the wort have proper O2? Did the wort have proper mineral balances? - it just keeps going.