Most biological ion channels demonstrate a high degree of selectivity for one type of ion more than others, and in many cases, how they control attaining this is still not clear. So we have studied on some metal ion compounds of glutamate. The Glutamate and its meal ion compounds (Ca2+, Na+, K+ and Li+) were first modeled by ab initio calculations and then Monte Carlo simulation was used to calculate solvation free energies and also the complexes free energies for the related structures. The results indicated that Glutamate-Ca2+ have more stability in water than other metal ion. Also, it was found out that the more movement in ions; less stability of the structure would result. This trend can be seen both in gas and liquid phase.