Propagation of surface plasma waves in a metallic single-walled carbon nanotube that either is encapsulated in a solid metallic channel or encapsulates a metallic nanowire are studied within the framework of the classical electrodynamics. The linearized hydrodynamic theory is used to describe the electronic excitations on the nanotube’s surface, while the dielectric function of dielectric media is modeled on the basis of the Drude approximation. It is shown that for all wavelengths, only the transverse magnetic wave with no angular dependence can propagate in these systems and the dispersion relations of this mode are obtained.