Metals are frequently present in active centers of enzymes.
Traditional ab initio methods have severe problems with transition metals. In fact, it can be proved that Hartree-Fock equation cannot be solved for the true metalic state. The DFT, similar to ab initio methods, is nonparametric, i.e., applicable to any molecule. While some say that basis sets are parameters for ab initio and DFT methods, this is an exaggeration. Basis sets are easily derived from atomic calculations, and beside, they were derived long time ago for all elements of periodic table.