  The nonbaryonic dark matter of the Universe is assumed to consist of new
stable forms of matter. Their stability reflects symmetry of micro world and
mechanisms of its symmetry breaking. Particle candidates for cosmological dark
matter are lightest particles that bear new conserved quantum numbers. Dark
matter particles may represent ideal gas of non-interacting particles.
Self-interacting dark matter weakly or superweakly coupled to ordinary matter
is also possible, reflecting nontrivial pattern of particle symmetry in the
hidden sector of particle theory. In the early Universe the structure of
particle symmetry breaking gives rise to cosmological phase transitions, from
which macroscopic cosmological defects or primordial nonlinear structures can
be originated. Primordial black holes (PBHs) can be not only a candidate for
dark matter, but also represent a universal probe for super-high energy physics
in the early Universe. Evaporating PBHs turn to be a source of even superweakly
interacting particles, while clouds of massive PBHs can serve as a nonlinear
seeds for galaxy formation. The observed broken symmetry of the three known
families may provide a simultaneous solution for the problems of the mass of
neutrino and strong CP violation in the unique framework of models of
horizontal unification. The existence of new stable charged leptons and quarks
is possible, hidden in elusive "dark atoms". Such possibility, strongly
restricted by the constraints on anomalous isotopes of light elements, is not
excluded in scenarios that predict stable double charged particles. The
excessive -2 charged particles are bound in these scenarios with primordial
helium in O-helium "atoms", maintaining specific nuclear-interacting form of
the dark matter, which may provide an interesting solution for the puzzles of
the direct dark matter searches. (abridged)
