Rare Earth Metals: Essential Resources for Modern Technology Rare earth metals refer to a set of 17 elements in the periodic table, specifically lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium. Despite their name, rare metals are relatively plentiful in the Earth's crust, with cerium being the 25th most abundant element....