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 shifted towards the millimeter-wave frequency band. Due to the wavelength of radiation, millimeter waves have several unique characteristics, which allow for both the active development of existing technologies and the creation of new ones that require high power or radiation energy. This article provides an overview of research on the application of millimeter waves to solve problems in physics, material 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, and the future development is also prospected.