Lockman's research interests include the structure and evolution of the Milky Way, and the structure of the interstellar medium. He is currently doing studies of gas flows into and out of galaxies, using the Green Bank Telescope and other instruments to make extremely sensitive measurements of neutral hydrogen beyond the disk of the Milky Way. He recently discovered that there is a cloud of gas falling into the Milky Way that contains enough gas to make more than a million new stars like the Sun. He is also involved in collaborations with scientists using the Planck satellite to study interstellar dust and the cosmic Infrared background.