The nature of metal and semi-conductor bonding has been investigated via UV photoelectron spectroscopy of cluster anions. Electrons from negative cluster ions of the desired mass are photodetached and then collected with the aid of judiciously arranged magnetic fields. Pulsed operation allows the use of time of flight techniques on both the parent ions and the photoelectrons. Photodetaching with UV grants access to the details of valence electronic structure. Our experiments show marked variations in electronic structure as a function of cluster size and composition. Cu cluster UPS show an even-odd alternation in electron affinities, predicted by cluster shell models. The UPS of sixty atom C Clusters corroborates the proposed soccerball structure for some C\sb60. Semi-conductor cluster UPS indicate shell closings for certain cluster sizes.