Metallic is the name of a storage or production-derived beer flaw that causes aromas and flavors of metal,tin, iron or blood. metal/iron/blood. Potential causes of this fault include contaminated water, contact with untreated or deteriorating brewing equipment, contact with untreated or deteriorating draft systems and non-passivated vessels. (Wine,Beer,Spirits,Sake,Mead/Tasting Terms Chemistry & Flaws)