  We review recent development in Raman techniques and diamond anvil cell
technology, that allow measurements of Raman of metals in the megabar pressure
range. The Raman technique includes holographic transmission optics and
single-stage spectrographs with CCD array detectors. Use of synthetic
high-purity diamonds and anglular excitation geometry reduces spurious
background scattering substantially, which makes observable very weak Raman
peaks in metals. We give several examples of studies including the hexagonal
close packed (hcp) $\epsilon$-Fe, Fe$_{(1-x)}$Ni${_x}$, and Re and the recently
discovered high-temperature superconductor MgB$_2$. The shift of phonon modes
with pressure is used for determination of the mode-Gr\"uneisen parameters,
estimation of shear elastic moduli and provide information on structural and
electronic transitions.
