The study of compact objects such as black holes and boson stars is an important component of modern astrophysics and particle physics. My talk will focus on two complementary aspects of the interplay between dark matter and compact objects. I will first discuss some indirect signatures that can be searched from bound structures formed of the QCD axion, a popular dark matter candidate. I will then focus on what we can learn on the properties of dark matter, light fields, and the structure of space-time from the observation of black hole phenomena like superradiance and VLBI interferometry.