The key element in QM/MM methods is the coupling term between the QM and MM regions. The most broadly employed coupling scheme is the so-called electrostatic embedding, in which the interaction between the QM region and the MM region is calculated with the QM electron density. This electron density is computed including the point atomic charges of each MM atom in the QM Hamiltonian. Recently, several hybrid ML/MM approaches have been proposed. Some of them rely on the so-called mechanical embedding approximation, in which the QM energies and forces are not corrected due to the presence of the MM systems, and accordingly the coupling term is calculated using partial atomic charges assigned to the QM region a priori. Other approaches aimed to recover the electrostatic embedding quality, both by somehow including the MM system in the ML framework, or by correcting in vacuo ML-predicted energies and forces using atomic polarizabilities. The stream of research focusing on atomic charges is extremely useful for the development of ML/MM schemes. The capability to predict atomic partial charges on the fly, along with energies and forces, would lead the path to new possible embedding schemes for ML/MM simulations. However, atomic partial charges do not correspond to an actual quantum mechanical observable, and there is not an unique way to assign them. The broad landscape of atomic partial charges ranges from sets derived from experimentally measured properties to sets computed from the electron density or molecular orbitals. Among the different proposed partial charges schemes, we can mention Electronegativity Equilibration Charges (EEQ), Mulliken, Minimal Basis Set-Mulliken (MBS-Mulliken), Natural Population Analysis (NPA), Intrinsic Bond Orbitals (IBO), Hirshfeld population analysis and related schemes (like Charge Model 5, CM5), Iterative Stockholder Approach (ISA), Minimal Basis Iterative Stockholder (MBIS), etc.