Overview of human metalloproteins and bacterial TBDTs discussed in this review. The cartoon depicts the competition between human host and Neisseria for iron and zinc. Metal withholding by human transferrin (Fe(III)), lactoferrin (Fe(III)), hemoglobin (heme Fe), and calprotectin (Zn(II)) occurs during infection. Neisseria hijack these host proteins for metal acquisition by expressing the TonB-dependent transporters TbpA, LbpA, HpuB, HmbR, CbpA, and TdfH. Calprotectin also binds Mn(II) and Fe(II), and Neisseria might be able to extract these metal ions from the protein in a similar fashion to that of Zn(II) acquisition.