We performed a study on the fundamental adsorption characteristics of Er₃NC₈₀ deposited on W(110) and Au(111) via room temperature scanning tunneling microscopy and spectroscopy. Adsorbed on W(110), a comparatively strong bond to the endohedral fullerenes inhibited the formation of ordered monolayer islands. In contrast, the Au(111)-surface provides a sufficiently high mobility for the molecules to arrange in monolayer islands after annealing. Interestingly, the fullerenes modify the herringbone reconstruction indicating that the molecule-substrate interaction is of considerable extent. Investigations concerning the electronic structure of Er₃NC₈₀/Au(111) reveals spatial variations dependent on the termination of the Au(111) at the interface.