To study the formation and the electronic properties of self-assembled dysprosium and erbium silicide nanowires on the vicinal Si(001) surface, we applied scanning tunneling microscopy and angle-resolved photoelectron spectroscopy. The formation of different types of nanowires was found, depending on the rare-earth exposure, postgrowth annealing temperature, and the rare-earth material itself. It is demonstrated that the so-called thin dysprosium silicide nanowires, which form close-packed arrays, are characterized by a nonmetallic band structure with negligible dispersion. In contrast to that, the so-called broad dysprosium silicide nanowires, which are lateral distances of several tens of nanometers apart, are metallic with one-dimensional electronlike bands crossing the Fermi energy. The effective masses of these bands amount to values ranging from 0.2 to 1.1 free-electron masses, and the overall band filling was found to be close to 1. It is shown that broad erbium silicide nanowires have a very similar electronic band structure compared to broad dysprosium silicide nanowires, while corresponding thin erbium silicide nanowires could not be found.