We investigated the [1.1.1]propellane molecule using the 3-D bond-path framework set B and the stress tensor B-sigma within the quantum theory of atoms in molecules (QTAIM). The controversial axial bond was determined to be a charge-shift bond comprising significant bond metallicity that correlated with values of the bond stiffness S < 1. The influence of the axial bond on the neighboring bonding is quantified in terms of unexpectedly low bond stiffness S values and a new measure of charge-shift bonding, the polarizability P. Consistency of these results was found at the MP2, CCSD and B3LYP theory levels.