Most of the time, free energy calculations are performed using molecular mechanics (MM) which is based upon the applied MMFFs. However, MM-based free energy methods sometimes cannot produce accurate energy values due to a lack of adequate description of some subparts of the simulation system with MMFFs, for which a QM-level description is often necessary. It is appealing to apply ML/MM MD approach to free energy calculations, given the advantage of ML over QM. In this framework, critical regions of a system, such as those being involved in chemical reactions and ligand and protein binding, are modeled with MLIPs, while the surrounding environment is modeled by MM. This approach enables high-quality free energy calculations as it strikes a balance between computational accuracy and efficiency.