In general, all known applications of high power microwaves directly use energy to interact with matter. In recent years, with the development of powerful millimeter-wave radiation sources, microwave technology has gradually drifted into the millimeter-wave frequency band. Due to the wavelength of radiation, millimeter waves have a number of unique characteristics, which allows both the active development of existing and the creation of new technologies that require high power or radiation energy. This article provides an overview of research work on the application of millimeter waves to solve problems in physics, materials science, biomedicine and others, including heating and diagnostics of thermonuclear plasma, processing and analysis of materials, biological effects, etc. The main difficulties arising in the implementation of the described tasks are presented, as well as future development is outlined.