This paper clarifies the effects of metal wires placed around a Multiple-Input-Multiple-Output (MIMO) array with the goal of improving the channel capacity in near-field MIMO systems. Tests are performed on dual-dipole arrays with metal wires placed parallel to the dipoles. If the antenna elements have an appropriate half-power beamwidth (HPBW), there is a clear improvement in the channel capacity of the dual-dipole array. The metal wires are used to increase the multipath richness and the locations of the wires significantly impact the channel capacity. A significant increase in the channel capacity is observed even if only one metal wire is placed in the proper location. We verified the generality of applying a metal wire to improve the channel capacity and that the improvement in the channel capacity is approximately proportional to the number of metal wires.