what medicine? antibiotic? How does your tongue look? Does it have a white "fuzzy" coat over it? This sounds like Thrush. its basically a yeast overgrowth on your tongue. It can cause a metallic taste. And occurs a lot from antibiotics and other medications.
use a tongue scraper, and there are special mouthwashes for it. You also want to take probiotics and reduce sugar and starch as the yeast feeds on that.