This chapter will describe the basic physical metallurgy applied to laser cladding and review the material systems that are being investigated for suitability in laser cladding processes. In the first section, the general cladability of substrate/clad materials will be described including both processing and metallurgical considerations. In the next section, a basic description of the relevant solidification conditions encountered during laser cladding will be completed. This will include the microstructural features that develop in the clad as a result of the solidification conditions. In the final section of the chapter, the material combinations that are most widely being investigated will be reviewed.