This chapter analyzes the electromagnetic modes supported by metallic grooves and wedges. Various approaches employed for the computation of the electromagnetic field in such structures are presented. The wave guiding properties are determined by means of rigorous electrodynamics techniques. Dispersion, modal size, shape, polarization, and propagation length of these modes is discussed. It is concluded that both channel and wedge modes are well confined and feature reasonable losses, wedge structures being favorable in terms of modal size.