In the previous chapter we developed a mean-field criterion for local magnetic moment formation in a metal. As mean-field theory is valid typically at high temperatures, we anticipate that at low temperatures, significant departures from this treatment occur. The questions we focus on in this chapter are: (1) how does the presence of local magnetic moments affect the low-temperature transport and magnetic properties of the host metal, and (2) what is the fate of local magnetic moments at low temperatures in a metal? These questions are of extreme experimental importance because it has been known since the early 1930s that the resistivity of a host metal such as Cu with trace amounts of magnetic impurities, typically Fe, reaches a minimum and then increases as – ln T as the temperature subsequently decreases.