Microcalorimetry is a useful tool for studies of heterogeneous catalysts, because it provides a direct measurement of the strength with which molecules interact with solid surfaces. The following communication reviews adsorption microcalorimetric studies of unsupported metals and metal-based catalysts performed over the last 20 years, and then presents three advanced microcalorimetric techniques and their applications to the study of low surface-area-metal single crystals, films and powders, and metal surfaces/catalysts that are highly reactive toward oxygenates.