We use molecular dynamics to calculate the vibrational density of states of several endohedral monometallofullerenes and compare the results with the experimental values. The vibrational patterns depend weakly on the charge transfer from the metal to the fullerene cage, with the largest variations of similar to 2 cm(-1) observed upon switching off completely the Coulomb interactions, and more strongly on the cage isomer, with variations of up to similar to 13 cm(-1). Analysis of the metal motions inside the cage shows that they can be chaotic. The origin of such chaotic behavior is discussed.