  We review some properties of black hole structures appearing in gravity with
a massless scalar field, with both minimal and nonminimal coupling. The main
properties of the resulting cold black holes are described. The study of black
holes in scalar-gravity systems is extended to $k$-essence theories, and some
examples are explicitly worked out. In these cases, even while the existence of
horizons is possible, the metric regularity requirement on the horizon implies
either a cold black type structure or a singular behavior of the scalar field.
