We have produced an endohedrally doped fullerene that shows a metal-like density of states at the Fermi level. Individual La@C-60 clusters deposited onto graphite exhibit a zero band gap as observed by scanning tunneling spectroscopy on single clusters at room temperature. Moreover, we find that an isolated La@C-60 cluster on graphite shows a reversible opening of a band gap at a transition temperature of similar to 28 K. The transition is associated with a freezing of the vibrational motion of the La atom inside the fullerene cage. The metallic behavior of La@C-60 is attributed to the presence of a dynamical dipole in the single cluster.