Understanding the cationic network and the medium range order of glasses and melts allows rationalization of each elements role in terms of the network former, charge compensator or network modifier concepts. Such knowledge can be combined with further details, e.g. regarding the role of highly coordinated network former elements, to model the macroscopic properties of glasses and melts, like their molar volume, density, configurational entropy and viscosity. In this chapter, we present recent advances on such work, which open new avenues for the production of useful and precise models of geologic and industrial glasses and melts.