  Massive stars, supernovae (SNe), and long-duration gamma-ray bursts (GRBs)
have a huge impact on their environment. Despite their importance, a
comprehensive knowledge of which massive stars produce which SN/GRB is hitherto
lacking. We present a brief overview about our knowledge of mass loss in the
Hertzsprung-Russell Diagram (HRD) covering evolutionary phases of the OB main
sequence, the unstable Luminous Blue Variable (LBV) stage, and the Wolf-Rayet
(WR) phase. Despite the fact that metals produced by ``self-enrichment'' in WR
atmospheres exceed the initial -- host galaxy -- metallicity, by orders of
magnitude, a particularly strong dependence of the mass-loss rate on the
initial metallicity is found for WR stars at sub-solar metallicities (1/10 --
1/100 solar). This provides a significant boost to the collapsar model for
GRBs, as it may present a viable mechanism to prevent the loss of angular
momentum by stellar winds at low metallicity, whilst strong Galactic WR winds
may inhibit GRBs occurring at solar metallicities. Furthermore, we discuss
recently reported quasi-sinusoidal modulations in the radio lightcurves of SNe
2001ig and 2003bg. We show that both the sinusoidal behaviour and the
recurrence timescale of these modulations are consistent with the predicted
mass-loss behaviour of LBVs, and we suggest LBVs may be the progenitors of some
core-collapse SNe.
