Various applications have attracted substantial attention to metamaterials due to their unusual electromagneticElectromagnetic properties. One such application is the development of polarizationPolarization converters and microwaveMicrowave absorbers. This chapter offers a thorough investigation of designs based on metamaterials. Frequency-Selective SurfacesFrequency-selective surface are the centre of attention as the research delves into the design and performance of broadband and multibandMultiband microwave absorbersMicrowave absorbers. An undecaband absorberUndeca-band absorber with consistent absorptionAbsorption characteristics, a triple-band absorberTriple-band absorber for C, X, and Ku-bandsKu-band, and a decaband absorberDeca-band absorber that can work as a reflectorReflector, spatial filterSpatial filter, and absorber are all important innovations. In addition, the book explores polarization convertersPolarization converters, novel broadband linear-cross andLinear-circular reflective polarizers linear-circular reflective polarizersReflective polarizers, and reconfigurable polarization convertersReconfigurable polarization converters that can operate in both reflection and transmissionTransmission modes. Several real-world applications can benefit from the proposed designs’ increased bandwidthBandwidth, polarization insensitivityPolarization insensitivity, and angular stabilityAngular stability, including wirelessWireless communicationCommunication systemsWireless communication systems, electromagnetic interference shieldingElectromagnetic interference shielding, and radarRadar cross-sectionRadar cross-section reduction. The results contribute to the development of technologies based on metamaterials and provide substantial enhancements to the performance of absorbersAbsorber and polarization converters.