RESUMEN
Looking for a perfect metallic behavior is a crucial research line for metamaterials scientists. This paper outlines a versatile strategy based on a contrast of dielectric index to control dissipative losses in metal within waveguides and resonant nanostructures. This permits us to tune the quality factor of the guided mode and of the resonance over a large range, up to eight orders of magnitude, and over a broad spectral band, from visible to millimeter waves. An interpretation involving a low-loss equivalent model for the metal is developed. The latter is based on a Drude model, in which the dissipative parameter can reach very low values, which amounts to a nearly perfect metallic behavior. Finally, this concept is applied to a practical design that permits us to finely control the localization of dissipation in an absorbing photonic structure.