  I will review the role of massive stars in galactic evolution both from the
nucleosynthesis and energetics point of view. In particular, I will highlight
some important observational facts explained by means of massive stars in
galaxies of different morphological type: the Milky Way, ellipticals and dwarf
spheroidals. I will describe first the time-delay model and its interpretation
in terms of abundance ratios in galaxies, then I will discuss the importance of
mass loss in massive stars to reproduce the data in the Galactic bulge and
disk. I will discuss also how massive stars can be important producers of
primary nitrogen if rotation in stellar models is taken into account.
Concerning elliptical galaxies, I will show that to reproduce the observed
[Mg/Fe] versus Mass relation in these galaxies it is necessary to assume a more
important role of massive stars in more massive galaxies and that this can be
achieved by means of downsizing in star formation. I will discuss how massive
stars are responsible in triggering galactic winds both in ellipticals and
dwarf spheroidals. These latter systems show a low overabundance of
alpha-elements relative to Fe with respect to Galactic stars of the same
[Fe/H]: this is interpreted as due to a slow star formation coupled with very
efficient galactic winds. Finally, I will show a comparison between the
predicted Type Ib/c rates in galaxies and the observed GRB rate and how we can
impose constraints on the mechanism of galaxy formation by studying the GRB
rate at high redshift.
