The biological sink for atmospheric methane consists of atmospheric methane-oxidizing bacteria (atmMOB) that persistently oxidize atmospheric methane as carbon and energy source and conventional methanotrophs that transiently oxidize atmospheric methane after exposure to elevated methane concentrations. The ecology and environmental activity of atmMOB have been studied for several decades, but until the first detailed characterization in 2019 of an atmMOB in pure culture that can grow with air as the sole energy (methane, carbon monoxide and molecular hydrogen) and carbon (methane and carbon dioxide) source, their physiology was mostly unexplored. Here we summarize the available knowledge about atmMOB physiology, including the kinetics of atmospheric methane oxidation, energy yields during growth on methane and other trace gases from air, carbon assimilation and physiological diversity. We use this background to identify knowledge gaps that should be targeted to support future research on atmMOB.