The electronic structure, band structure and optical properties of compounds GaAs(1−x)Mx (M = Fe,Cu), for x=0.25, 0.75, and 1 are discussed via Full-potential linearized augmented plane wave calculations. An increase in absorption in the visible spectrum is observed for all compounds, which, however, is associated with an increasingly metallic character as the metal concentration increases, to the point that compound GaFe is an indirect degenerate semiconductor. The addition of Fe and Cu to the compound decreases its stability, as demonstrated by the formation enthalpies, which become progressively more positive as the content in As is decreased. The calculations were performed using both the PBE and PBEsol exchange correlation potentials and the TB-mBJ method was used to verify the band structure obtained.