The electronic structure and spin asymmetry of metal phthalocyanines (Pcs) (metal=Mn, Fe, Cu, and Mg) and metal-free PC thin films of 1-monolayer (ML) thickness on an Fe(100) substrate were investigated using spin-polarized metastable deexcitation spectroscopy (SPMDS). The surface density-of-states (SDOS) cif these Pcs observed in MDS was almost identical, and thus, insensitivity of the PC electronic structure to the variation of the central metal atoms is indicated. On the other hand, the spin asymmetry in the SPMDS measurements exhibited noticeable differences among Pcs. These results are discussed from the viewpoint of the Pcs electronic structure calculated by a discrete variational X alpha method. The fact that differences are found in the spin asymmetry but not in SDOS among Pcs indicates an important role of the central metal atoms for spin polarization.