Metallic glasses can be prepared by solidification of liquid alloys at cooling rates sufficient to suppress the nucleation and growth of competing crystalline phases. This Article presents a historical survey of the study of metallic glasses and other amorphous metals and alloys. This includes a discussion of synthesis and processing methods, structure and morphology, and a description of the electronic, magnetic, thermodynamic, chemical, and mechanical properties of metallic glasses. In addition, the Article describes the development of metallic glasses as materials for technical applications.