In order to build lean muscle, it is important to engage in regular resistance training using compound exercises such as squats, presses, and rows. Alongside this, follow a high-protein diet with slightly more calories than you burn, aim for progressive overload, and make sure to prioritize rest and sleep as muscle growth occurs during recovery periods. Emphasize consuming whole foods, staying hydrated, and minimizing the intake of unhealthy junk food to achieve a lean muscle gain.