Drude model. Electron gas: Sommerfeld expansion, Landau levels. Structure factor. Crystals, 2d and 3d lattices. Reciprocal lattice. Electrons in a periodic potential: Bloch Theorem. Weak periodic potential, tb method. OPW and pseudopotential. Electrons and holes, Effective mass, Bloch oscillations. Interacting electrons: H and HF equations. Screening. Quantum theory of harmonic solids. Electron-phonon interaction in metals.