We have grown semicontinuous and continuous metal films on silica nanoparticles. These nanostructures exhibit distinct spectral and dynamical optical signatures of the percolation threshold. Using time-resolved pump-probe measurements, we have investigated the electron dynamics in the semicontinuous metal layers. The observed electron dynamics are dramatically different than in continuous metals, exhibiting an initial rapid relaxation which we attribute to the equilibration of electrons in localized surface plasmons or 'hot spots' with electrons throughout the film. (C) 2002 Published by Elsevier Science B.V.