In recent years increasing interest has focused on the use of photonic and metamaterial structures for microwave applications. Predominately this work has focused on the development of novel antenna based technologies. Recently interest has grown into the possible use of photonic and metamaterials for high-powered microwave applications. In this paper we consider the use of photonic and metamaterial structures for applications such as; travelling wave-structures, RF generation, standing wave resonators and applications diverse as inverse Cherenkov accelerators. We review the physical processes and length scales that define photonic crystals and metamaterials, and introduce a theoretical approach to describe the interaction between charged particles and these structures. We also discuss the advantages photonic and metamaterials offer such as; high mode selectivity, zero-reflection, selective phase shifting, novel dispersion relationships, and effective negative permittivity / permeability. Discussing the advantages photonic crystal and metamaterial based technologies offer compared to their conventional counterpart