  We study several aspects of electroweak vacuum metastability when an extra
gauge singlet scalar, a viable candidate for a dark matter particle, is added
to the standard model of particle physics, which is assumed to be valid up to
the Planck scale. Phase diagrams are drawn for different parameter spaces, and
based on that, we graphically demonstrate how the confidence level, at which
stability of electroweak vacuum is excluded, depends on such new physics
parameters.
