Photoelectron spectroscopy, with LEED, Auger electron spectroscopy (AES) and secondary electron emission crystal current (SEECC) measurements, has been used to investigate the electronic structure of well-characterized overlayers of Tl, Cr, Mn and Fe on Ag(100) and Fe on Cu(100). The Stranski-Krastanov growth mode has been found for Tl on Ag(100). In the chain structure observed at 70 K, there is no evidence for a Peierls distortion, in contrast to Tl chains on Cu(100). Band-mapping of the Tl 6p band has indicated the absence of an energy gap at the Fermi level, confirming the LEED result that the Peierls distortion has been suppressed. This is believed to be due to commensurability with the substrate. A study of Cr on Ag(100) has revealed epitaxial growth up to two monolayers, with a transition to bilayers before the completion of the first layer. Photoemission measurements of the Cr 3s multiplet splitting indicate an enhanced magnetic moment, which approaches the bulk value with coverage. This enhancement is thought to be a consequence of d-band narrowing, resulting from the reduced dimensionality of the overlayer. A p(1 x 1) surface alloy is initially observed when Mn is deposited on Ag(100), but with a magnetic moment smaller than the bulk Mn value; angle-resolved photoemission measurements indicate significant overlayer- substrate d-d interaction, in contrast to Cr on Ag(100). With further coverage, the magnetic moment increases and when simultaneous multilayer growth occurs on the AgMn surface, the bulk value is attained. Pseudomorphic 1ayer-by-layer growth has been identified for Fe deposited on Cu(100) and the band structure has been determined for Fe coverages of one and seven monolayers. From a comparison with calculated band structures, it is proposed that the monolayer is ferromagnetic, while the thicker fee film may be antiferromagnetic. An Fe monolayer on Ag(100) has also been shown to have ferromagnetic order.