First-row transition elements are essential for all forms of life. During infection invading microbes must obtain these nutrients from their host. Vertebrates take advantage of this fact to combat invaders by sequestering essential nutrients, a defense known as nutritional immunity. The most well-characterized aspect of this defense is the iron-withholding response. Advances in elemental imaging have revealed that zinc and manganese are also sequestered during infection. The importance of nutritional immunity to host defense is emphasized by the increased susceptibility to infection when levels of these metals are elevated. This chapter will discuss iron, zinc, and manganese availability during infection, the impact of withholding these metals from invading pathogens, and the antimicrobial peptides utilized by the host to restrict the availability of these essential nutrients.