In this paper electromagnetic properties of periodic arrays of single-wall metallic carbon nanotubes (CNs) are presented. Semiclassical model, based on periodic Green's function, which takes into account electromagnetic interaction between nanotubes, is developed. Quantum properties of nanotubes are taken into account via the complex conductance. Propagating and evanescent eigenwaves in infinitely long CNs are studied. Strong dependence of the slow-wave factor on the transversal wave vector and considerably low attenuation is demonstrated. A plane wave transmission through a slab of CNs at terahertz frequencies is considered.