This work introduces a novel approach to improve the performance of a patch antenna by integrating metamaterials (MTM). The design features a rectangular patch antenna with a defected ground, operating at 3.58 THz, mounted on a silicon dioxide (SiO2) substrate characterized by a dielectric of 4 and a thickness of 2 µm. Beneath the antenna, a metamaterial layer consisting of 6 × 5 elements is strategically placed to enhance its performance. The integration of MTM leads to significant improvements in the antenna’s performance, including better impedance matching and increased directivity. Specifically, the return loss improves from −14.00 dB to −55.15 dB, the gain rises from 2.84 dB to 5.25 dB, and directivity increases from 4.60 dB to 6.87 dB. These enhancements are achieved due to the unique electromagnetic behavior of the MTM layer, which aids in minimizing back radiation and focusing the radiated power. The simulation results, obtained using HFSS software, validate the effectiveness of the proposed MTM-based antenna design for potential applications in advanced 6G communication systems and biomedical devices.