Mistborn is a fantasy book about people with magical abilities called allomancers.
Allomancers "burn" (metabolize metals in the body for magical powers) ingested metals, thereby enhancing various physical and mental capacities.
An duralumin allomancer is referred to as a gnat or duralumin gnat. A Mistborn that burns duralumin causes a reaction with any of the other metals they are currently burning to create an exceptionally large flare of the metal, consuming the remaining supply. The exact degree to which duralumin enhances the next metal burned is unknown but appears to be massive.