The dielectric and magnetic properties of materials are foundational to the functionality, efficiency, and reliability of radio frequency and microwave devices, underpinning technologies ranging from communication networks to sensing and industrial equipment. This article aims to establish a comprehensive link between the fundamental properties of materials and their practical performance in such devices. It first elaborates on the core theories of dielectric properties and magnetic properties, as well as key influencing factors including frequency and environmental conditions. Subsequently, it classifies dielectric materials and magnetic materials based on their characteristic properties and application scenarios. The core section details the impact of these material properties on critical radio frequency and microwave devices such as antennas, filters, isolators, microwave absorbers, and oscillators. Additionally, standardized testing methods for dielectric and magnetic properties are systematically presented. Finally, the article addresses current challenges including high-frequency loss, material compatibility, and temperature stability, while highlighting emerging trends such as nanocomposites, tunable materials, and green/sustainable materials. This work serves as a valuable resource for professionals and researchers in material selection, device design, and technology development, providing insights to align material characteristics with application requirements and driving the advancement of radio frequency and microwave technologies.