Parameters of Morse potentials for describing the interactions of atoms of light elements C, N, O with atoms of fcc metals Al, Ag, Ni are found. This set of three metals is unique in that two of them have almost the same radii of atoms, while the other two have almost identical electronegativities. The search for potential parameters was carried out according to the empirical relationships observed for a large number of metals having C, N or O impurities. For this purpose, the most studied characteristics were chosen: the melting or decomposition temperature of the corresponding chemical compound of the metal with the light element and the activation energy of diffusion of the impurity atom in the crystal lattice of the metal. In the paper, in addition, we have corrected the potentials found earlier to describe interatomic interactions in Pd-H and Ni-H systems.