  First principle band calculations based on local versions of density
functional theory (DFT), together with results from nearly free-electron
models, can describe many typical but unusual properties of the high-$T_C$
copper oxides. The methods and a few of the most important results are
reviewed. Some additional calculations are presented and the problems with the
commonly used approximate versions of DFT for oxides are discussed with a few
ideas for corrections. It is concluded that rather modest corrections to the
approximate DFT, without particular assumptions about strong correlation, can
push the ground state towards anti-ferro magnetic (AFM) order. Spin
fluctuations interacting with phonons are crucial for the mechanism of
superconductivity in this scenario.
