High-velocity clouds (HVCs) consist of gas that does not take part in normal Galactic rotation, having velocities deviating by up to 400 km s−1 from those expected from rotation. Over the past five decades, studies have shown they these clouds trace a number of different processes, including the Galactic Fountain, tidal streams, and infall. Here, I summarize some recent results concerning measurements of cloud metallicities and distances and how these are used to understand individual clouds and derive the conclusion above.
