  We investigate instabilities in the charge channel in the vicinity of
(meta-)magnetic transitions of itinerant electron systems. Based on a weak
coupling analysis we argue that in a one-band $t$-$t'$ Hubbard model near the
van Hove filling and dominant ferromagnetic fluctuations it is difficult to
account for a microscopic mechanism for a d-wave Pomeranchuk deformation of the
Fermi surface. A similar deformation has been considered for the metamagnetic
transition in Sr$_3$Ru$_2$O$_7$. As an alternative we discuss the possibility
of charge inhomogeneity on the nano scale. This extends the analogy of the
metamagnetic transition to a liquid-gas transition.
