Mn is deposited on the (0001) surface of Ru and the (100) surfaces of Fe and Ni in a PHI 400 molecular-beam epitaxy system. The first two layers of Mn on Ru (0001) maintain the close-packed spacing of the Ru substrate. By comparison with other forms of Mn, this is an expanded structure. Beyond two layers, Mn maintains epitaxy, forming a denser phase which is most likely the hexagonal Zn2Mg structure, but possibly the fcc Cu2Mg structure, or a stacking fault variant of these two quite similar structures. The basic unit of both the Zn2Mg and Cu2Mg structures is the hexatetrahedron which is found also in the more complex α-Mn structure. In each of these cases Mn appears to be an intermetallic compound with itself. Mn on Fe(100) forms epitaxially in the bcc phase. Mn on Ni(100) forms in a complex phase which has yet to be deciphered. The atomic magnetic moments of the Mn atoms in these phases are deduced from measurements of the exchange splitting of the 3s peak in the x-ray photoelectron spectra. The splitting of the 3s peak is surprisingly insensitive to the Mn structure, but the intensity of the split-off peak reflects the dependence of magnetic moment to atomic volume.