A low temperature scanning tunneling microscope (STM) was used to probe the bonding of CO on NiAl(110) and the formation of PdCO and Pd(CO)(2) at the single molecule level. While tilting of the two ligands is expected for Pd(CO)(2), the observed bending of the CO molecule in PdCO is surprising. The combination of real space topographic imaging and spatially resolved vibrational spectroscopy in a STM provides a unique method in revealing internal bonding configuration and vibrational properties of individual metal carbonyls.