Magnetic materials are broadly classified into two groups with either hard or soft magnetic characteristics. Soft magnetic behavior is essential in any application involving changing electromagnetic induction such as solenoids, relays, motors, generators, transformers, and magnetic shielding. This Article provides a description on ferromagnetic properties, the effect of impurities, alloying additions, heat treatment, residual stress, and grain size on magnetic properties. It also describes the alloy classification and magnetic testing methods of soft magnetic materials, which include high-purity iron, low-carbon steels, silicon steels, iron-aluminum alloys, nickel-iron alloys, iron-cobalt alloys, ferrites, and stainless steels. The Article discusses the corrosion resistance of soft magnetic materials, and provides information on selection of alloys for power generation applications, including motors, generators and transformers. It concludes with a short note on design and fabrication of magnetic cores.