GaN based materials have continued to be at the forefront of spintronics research due to the demonstration of room temperature ferromagnetism in these materials. A goal of this research is the fabrication of spintronic devices that may provide easy incorporation into existing GaN processing technologies, higher integration density, and less power consumption than their electronic counterparts while achieving similar speeds. The progression of the ferromagnetic metals incorporated into GaN has moved from transition metals to rare earth metals such as the lanthanides. In this chapter, we review this progression for material selection as well as methods of their incorporation and models for the mechanism for ferromagnetism in these materials.