When tasting beer, not everything is black and white. Lagers should be clean, but English ales are expected to have something of a fruity profile, Belgian ales even more so. Oxidation is generally undesirable, except in those occasional situations when it transforms a big barleywine into a sublime sherry-like sipper. What’s considered an off flavor in one beer style may very well be welcome in another, at least in moderation.
There is no gray area, however, when it comes to metal: Nobody wants to drink metallic tasting beer. Small amounts might remind you of that bloody I-just-bit-my-tongue-again flavor, while larger amounts can evoke images of having just sucked on a penny.
Metallic flavors usually come from—surprise!—metal. The key to eliminating them is, therefore, to remove potential sources of metal contamination from your process. Depending upon your own particular system, beer might come into contact with metal from mash tun and kettle to fermentor and faucet (and all points in between). Here are a few things to consider if your beer tastes metallic.