I get that funny metalic taste, but just try to ignore it best I can. I also think it is more than just contact with the tongue, because I could taste it even when I got it IV. I would be sleeping and would wake up when they started the drip, and told the nurse, "you're hanging the Flagyl now, right? Because, I can taste it..."
But' for me the best way to deal with it is by putting something tasty in my mouth, like hard candies, mints, etc.