Drucker yield function in a form of the second and third stress invariants is transformed into an anisotropic form by introducing a fourth order linear tensor. The effect of the third stress invariant is calibrated for BCC and FCC metals. The anisotropic yield function is applied to model anisotropic yielding of AA2008 T4. The proposed yield surface is compared with those of the Hill48 and Yld2000-2d yield functions. The comparison with experimental data and other yield functions validates the accuracy of the proposed yield function. The anisotropic Drucker function also can model anisotropy under spatial loading with ease. Thus the yield function proposed is suggested to model the anisotropy of metals not only under plane stress but also under spatial loading.