How does the conductivity of any material vary with density

We know the relation of resistivity with its length, area. But what will happen if we increase or decrease mass density of material.

Will the mean free path be changed? Will the electrons gain more thermal energy because more collisions?

If we imagine the situation then it seems like electrons are crowded like many peoples in a small room. Is it correct imagination?

Density means we are slowly compressing the material.