Metallic oxide compounds have interesting applications in catalysis, in optoelectronics, and as sensitive detectors. One of these, RuO2, is also an excellent material for charge storage. Composite core–shell nanowires formed by an inner insulating SiO2 wire serving as scaffold to an external RuO2 nanotube have promising uses. Electronic structure calculations reveal an interesting modification of the electronic band structure of the external oxide shell induced by the presence of the SiO2 core. The small changes in the interatomic distances in RuO2 as it adapts to the underlying core lead to some bands crossing the Fermi level, and to an enhancement in the metallicity of the system. As a consequence, a substantial increase of the conductance of the wires is predicted when the composite SiO2@RuO2 wires are accommodated between two gold electrodes. The result suggests that the small strain occurring as metal oxide wires adapt to the insulating core can be used to tailor the electrical conductance.