Relationship between electrical resistivity and density

There is no relationship between the density of a metal and its electrical resistivity.

There is a big database of material properties called MatWeb which is recommend as a legitimate source of data by UCSD's and Stanford's library systems, Rose-Hulman, etc.

I took data from around 60 different metals and graphed them:

As you can see there is no empirical relationship. From a theory perspective, density has to do with atomic packing and resistivity has to do with electronic structure.

I will admit, however, that gaseous copper is an extremely poor conductor.