In recent years, the emerging areas of nanophotonics and, in particular, plasmonics and metamaterials, have seen an explosion of novel ideas. However, transforming revolutionary designs into practical devices requires a significant amount of effort. The constituent materials in plasmonic structures and metamaterials play a crucial role in realizing useful and efficient devices. Similar to the way silicon shaped the nanoelectronics field, finding the best set of materials for plasmonic and metamaterial devices could revolutionize the field of nanophotonics. As a potential solution, alternative plasmonic materials have recently gained significant attention. Metals, despite being essential components of plasmonic and metamaterial devices, pose many technological challenges toward the realization of practical devices—primarily due to their high optical loss, integration, and fabrication limitations. Hence, searching for an alternative is vital to the success of future nanophotonic devices. Several classes of materials, including doped semiconductor oxides and ceramics, are discussed as potential alternatives to metals that could lead to devices with drastically improved performance and new functionalities by providing low intrinsic loss, tunability, and compatibility with standard semiconductor fabrication processes.