Placing any metal close to the microstrip patch designed without ground, would act as a ground and will decrease the bandwidth of the antenna. A standard patch antenna with ground have BW about 5%.
An option would be to use a pattern ground (search the net for a shape) placed at relative high distance from the patch, but this will require intensive EM simulation to get the optimum.
Other option that increase the BW of the patch antenna (other than dielectric height and type, or adding parasitic patch elements) is to place a ground at some distance and a U-shape slot into the patch. This also require EM simulation.