I'm a little confused by the description I commonly hear about the electron counting rule in band theory. The general statement I find is that a "solid with an odd number of electrons per unit cell is a metal, while an even number of electrons could be an insulator or a metal". However, in materials such as CuO and VO2, there are two or more (even number) of formula units per unit cell, so regardless of, e.g., VO2 having a 3d1 configuration, two formula units would mean two d1 electrons and therefore an even number of electrons per unit cell. For some reason, "counting arguments" still imply that these materials should be metals, but I'm not sure how this is the case if the number of electrons per unit cell is the determining factor (according to band theory). I think this rule must be misstated. Can someone clear this up for me?
Note: I am aware that these are NOT metals - I'm just trying to understand why the band theory "counting argument" would suggest that they are.