  Experimental searches for pure glueball states have proven challenging and so
far yielded no results. This is believed to occur because glueballs mix with
the ordinary $q\bar q$ states with the same quantum numbers. We will discuss an
alternative mechanism, the formation of the glueball-meson molecular states. We
will argue that the wave functions of already observed excited meson states may
contain a significant part due to such molecular states. We discuss the
phenomenology of glueball-meson molecules and comment on a possible charmless
component of the $XYZ$ states.
