  There exist several types of monopole - like topological defects in
Electroweak theory. We investigate properties of these objects using lattice
numerical methods. The intimate connection between them and the dynamics of the
theory is established.
  We find that the density of Nambu monopoles cannot be predicted by the choice
of the initial parameters of Electroweak theory and should be considered as the
new external parameter of the theory. We also investigate the difference
between the versions of Electroweak theory with the gauge groups $SU(2)\otimes
U(1)$ and $SU(2)\otimes U(1)/Z_2$. We do not detect any difference at $\alpha
\sim {1/128}$. However, such a difference appears in the unphysical region of
large coupling constant $\alpha > 0.1$.
