Metals (iron, zinc, nickel, cobalt, etc.) participate in numerous enzymatic reactions and are essential nutrients for bacteria. Inside our organism, but these metals are scarcely available, because they are bound to proteins which preserve and transport them to the cells and tissues where they will be used.

During the infection process, bacteria compete with the organism in obtaining these metals. The response to metal starvation is often very virulent, bringing on strategies aimed to increase the supply of these elements. Metal acquisition is often achieved by releasing toxins, proteins that bind metals with high affinity and transporters that introduce these metals into the bacteria. In essence, these are highly sophisticated virulence mechanisms aimed at guaranteeing the support of essential nutrients needed for the bacteria's survival.