Generally I would advise against combining two seemingly irrelevant potentials together in simulations of complex systems. Although this is possible via LAMMPS’ pair_style hybrid and variants, this requires significant knowledge of how the two potentials are constructed and parameterized. Simply mixing-and-matching in most cases would fail – meaning yielding bad potential (or force field) parameters resulting in bad dynamics.
Please keep my warning in mind. Meanwhile, it is easier to change the real units for the polymer force field to metal units. EAM potential file is notoriously complicated with too many pitfalls to fall through if you change the unit style.
Hope this helps.
Ray