Chemistry and physics of the rare earth elements and their compounds are in a rapidly expanding state of development. Many new materials with interesting magnetic properties have recently become available. The potential of lanthanon compounds as magnetic materials in electrical engineering is evaluated by comparing the basic properties of lanthanons and transition metals. The lanthanides show certain unique properties resulting from the localization of their magnetic4flevels. Unfortunately, their Curie temperatures are relatively low. The probability of finding ferromagnetic lanthanide compounds with high Curie temperatures is explored. A survey of magnetic properties of metallic and nonmetallic lanthanide materials indicates possible applications for which they can compete favorably with other materials.