  Organic liquid scintillators are used in many neutrino physics experiments of
the past and present. In particular for low energy neutrinos when realtime and
energy information are required, liquid scintillators have several advantages
compared to other technologies. In many cases the organic liquid needs to be
loaded with metal to enhance the neutrino signal over background events.
Several metal loaded scintillators of the past suffered from chemical and
optical instabilities, limiting the performance of these neutrino detectors.
Different ways of metal loading are described in the article with a focus on
recent techniques providing metal loaded scintillators that can be used under
stable conditions for many years even in ton scale experiments. Applications of
metal loaded scintillators in neutrino experiments are reviewed and the
performance as well as the prospects of different scintillator types are
compared.
