The electronic structure of the formally ${\mathrm{Cu}}^{3+}$ metallic ${\mathrm{LaCuO}}_{3}$ has been studied by photoemission and x-ray-absorption spectroscopy. By analyzing the valence-band and Cu $2p$ core-level photoemission spectra using a ${\mathrm{CuO}}_{6}$ cluster model, the charge-transfer energy is estimated to be $\ensuremath{-}1\mathrm{eV},$ indicating that the ground state is dominated by the ${d}^{9}L$ configuration with which the ${d}^{8}$ configuration is strongly hybridized, where $L$ denotes a ligand hole. However, agreement between the experimental results and the cluster-model calculations is not satisfactory for the detailed line shape of the main peaks. Especially, the Cu $2p$ x-ray-absorption spectrum cannot be well explained by the single-site cluster-model calculation, suggesting the importance of intercluster interaction. On the other hand, the existence of the charge-transfer satellite in the Pauli-paramagnetic state is explained by Hartree-Fock band-structure and self-energy calculations using parameters deduced from the analysis of the photoemission spectra.