Ridge waveguide metamaterial filter comprising at least one ridge waveguide, at least one microwave or millimeter wave metamaterial-filter and at least one transition structure. The metamaterial-filter comprises a host waveguide including a plurality of radiatively coupled resonant elements, the plurality of radiatively coupled resonant elements being configured to provide radiatively coupled local resonators and a subwavelength guided mode of the metamaterial-filter providing a frequency passband for transmission of a selected or filtered electromagnetic wave signal through the metamaterial-filter. The transition structure is located between the ridge waveguide and the one metamaterial-filter, and is configured to guide the input electromagnetic wave to the at least one metamaterial-filter and radiatively couple the input electromagnetic wave to at least one resonant element or a first resonant element of the at least one metamaterial-filter.