In this paper, we explore ways to model metalloproteins with ligand-coordinated metal sites using RBFE with open-source tools. Recent commercial force fields, such as OPLS-5 discusses improved modeling capabilities for metals, but are not available open source. We tested two force field approaches for modeling coordinating metals in RBFE calculations for metalloproteins. While we look at divalent zinc proteins, the strategies proposed can be applied to other metalloproteins but will need further validation.