  Within the scope of a spherically symmetric space-time we study the role of
different types of matter in the formation of different configurations with
spherical symmetries. Here we have considered matter with barotropic equation
of state, scalar field, electromagnetic field and an interacting system of
scalar and electromagnetic field as the source. Corresponding field equations
are solved exploiting harmonic coordinates. An easy to handle method is
proposed which allows one to have an idea about the possible behavior of the
metric functions once the components of the EMT of the source field is known.
