Molybdenum was recognised in 1778 by Carl Wilhelm Scheele, who showed that the mineral molybdenite was not a lead ore as had been assumed, and the metal was isolated in 1781 by Peter Jacob Hjelm. The name records the very confusion Scheele dispelled: it comes from the Greek molybdos, meaning lead. Molybdenum is a hard, silvery, extremely high-melting metal, valued for strengthening steel and as an essential trace element in living enzymes. Its high melting point makes molybdenum valuable in steels and superalloys for engines, tools and furnaces and as a catalyst in refining petroleum, while as a trace nutrient it sits at the active centre of enzymes in plants, animals and bacteria, including those that fix nitrogen.
Hjelm produced the first metallic molybdenum in 1781 by reducing molybdic acid with linseed oil and carbon in a sealed crucible, a method Scheele himself had specifically asked him to try, lacking a furnace that could reach the necessary temperature. The metal found unexpected strategic importance in the First World War, when Germany, cut off by blockade from adequate tungsten supplies, substituted molybdenum in artillery and armour steel and found it performed comparably at a fraction of the weight, a wartime discovery that permanently established molybdenum as a standard alloying element in high-strength steels rather than a mere tungsten substitute.