Bulk metallic glasses attracted the attention of the materials research community after the breakthrough achieved from the end of the 1980s to the beginning of the 1990s. The high glass-forming ability (GFA) of some alloys allowed the formation of bulk metallic glasses upto about 80. mm in size by using various casting and water cooling processes. Owing to the absence of a crystalline lattice and defects such as dislocations, a unique deformation mechanism is realized in these materials, which thus exhibit high strength, high hardness, good wear resistance, and large elastic deformation. In this chapter, we describe the research achievements in the field of bulk metallic glasses and review their formation mechanism, GFA, structure, thermal stability, deformation behavior, corrosion resistance as well as their soft and hard magnetic properties. A special emphasis is given to ferrous metal-based soft magnetic Fe- and Co-based BMG alloys as well as hard magnetic Nd-based alloys.