This work is focused on the investigation of the influence of the fluctuations in the electronic charge density of metal clusters and fullerenes in response to an approaching charged particle. Analyzing the electron- and positron-impact ionization of C₆₀ and metal clusters we show that the account of the dynamic polarizability explains the suppression of the ionization channel in the low-energy region of spectra. The interrelation between the finite size of Li clusters and nonlocal screening effects is investigated as changes in the ionization cross sections with increasing cluster radius. The role of the exchange interaction is considered by comparing the cross sections for the positron-impact ionization of clusters with the respetive cross sections when electrons are used as a projectile.