The hypothesis that dark matter can be described through ultra-light scalar fields has received considerable attention in recent years. Such matter would interact with astrophysical objects, such as black holes. In this scenario it becomes interesting to study how scalar fields interact with black holes. These studies also act as proxy models for more complex cases, such as for interactions with fields with non-zero spin. In this work we consider the absorption of scalar fields by static and stationary black holes numerically, finding also analytical results in the high- and low-frequency limits. We investigate bound states in this context, as well, showing that scalar modes with a certain frequency are trapped around the black hole. Such solutions are dubbed 'clouds' and indicate the presence of hairy solutions.