We present the density functional calculation results for K adsorption on the Pt(111) and Cu(111) surfaces in a (2 × 2) structure. The site preference, surface relaxation, and electron structure of these systems are analyzed. The hcp hollow position is found to be the most favorable for K adsorption on Pt(111). For the Cu(111)-(2 × 2)-K system we find that all the considered adsorption sites (hcp and fcc hollow, bridge, and top) lead to the energy difference within few meV. The calculated surface relaxations and adsorption geometry are in agreement with available experimental data. It is demonstrated that the K adsorption leads to the disappearance of a number of the substrate surface and resonance states in the energy region above − 2 eV/−3 eV (Pt/Cu) and to the appearance of new surface features, as well as bands that are significantly localized at the adsorbate. It is found that the K adsorption (1) transforms the Shockley surface state lying in the bulk band gap near the Γ point on the clean Pt and Cu surfaces into the state localized at the K adlayer and (2) and shifts this state up by energy about 0.4 eV.