We present a theoretical modeling of the electron energy loss spectroscopy data for monolayer graphene supported by Pt(111), Ru(0001), and Ni(111) substrates. In order to reproduce the experimental loss function, we have used a two-dimensional, two-fluid hydrodynamic model for inter-band transitions of graphene’s π and σ electrons and an empirical Drude-Lorentz model in the local approximation for metal substrates. The agreement between the theoretical curves and the experimental data is very good in the cases of graphene supported by Pt and Ru substrates. Conversely, the agreement is less satisfactory for the case of graphene/Ni, presumably due to the strong hybridization between the π states of graphene and the d bands of Ni, which is not accounted for in the model.