  We discuss various models and scenarios proposed to explain the nature of the
V838 Mon type eruptions. In this class of eruptive objects we include: M31 RV
(erupted in 1988), V4332 Sgr (erupted in 1994) and V838 Mon (erupted in 2002).
We concentrate on three models: (i) thermonuclear runaway on an accreting white
dwarf (nova-like event); (ii) He-shell flash in a post asymptotic giant branch
star (born-again AGB); and (iii) merger of stars. We show that models (i) and
(ii) cannot account for the majority of the observed properties of the objects.
Most significantly, in both nuclear burning type models the object is expected
to heat up before declining and fade as a very hot compact star. In the
observed eruptions the objects declined as very cool giants or supergiants. We
show that the stellar merger model can account for all the observed properties
and conclude that presently this is the most promising model to explain the
eruptions of the V838 Mon type.
