In this paper, a sub-6 beam-steerable antenna array system is introduced. The main radiating element in the proposed array is a gain-enhanced Vivaldi antenna, whose overall realized gain is improved by introducing near-zero-index metamaterial (NZIM) with broadband characteristics at 3.6 GHz. The proposed system is intended to be integrated with fifth-generation automotive applications. The 4 × 4 butler matrix is resonating at 3.6 GHz to feed the designed antenna array elements and steer the radiating beam. When altering the phase of the input signal, the primary beam direction is steered at an angle from 45° to 135°. So, by choosing the butler matrix input port, the phase of each radiating element is changed, which leads to precise beam direction control. All the system components, including antenna elements and the [4 × 4] butler matrix, are designed, simulated, and optimized. In order to verify the proposed design, the system is fabricated using the photolithographic technique. The experimental results show very good agreement with the simulated ones. The NZIM-loaded antenna element achieves a − 10 dB bandwidth of 2.9 GHz, while the overall array system achieves a 600 MHz bandwidth. The steered beam of the proposed system has an overall realized gain of 11.2 dB.