  First-principles calculations of the inelastic lifetime of low-energy
electrons in Al, Mg, Be, and Cu are reported. Quasiparticle damping rates are
evaluated from the knowledge of the electron self-energy, which we compute
within the GW approximation of many-body theory. Inelastic lifetimes are then
obtained along various directions of the electron wave vector, with full
inclusion of the band structure of the solid. Average lifetimes are also
reported, as a function of the electron energy. In Al and Mg, splitting of the
band structure over the Fermi level yields electron lifetimes that are smaller
than those of electrons in a free-electron gas. Larger lifetimes are found in
Be, as a result of the characteristic dip that this material presents in the
density of states near the Fermi level. In Cu, a major contribution from $d$
electrons participating in the screening of electron-electron interactions
yields electron lifetimes which are well above those of electrons in a
free-electron gas with the electron density equal to that of valence ($4s^1$)
electrons.
