The following work details a novel enhancement to metal detector coil designs with the intent of advancing the state of the art for large-scale, free-flowing threat detection in pedestrian traffic. The enhancement is achieved by increasing the signal-to-noise ratio through shaping the magnetic field and concentrating the magnetic flux to one side. Commercial metal detectors used for security suffer from decreased range and sensitivity when operated in the vicinity of benign metallic objects (e.g. rebar, metal studs, fencing, electrical wires, etc.) that generate unwanted signals. A Halbach array design provides passive enhancements by increasing the relative flux density in the direction of interest with limited additional supporting electronics. Halbach array coils were characterized and compared with single pulse induction coils for changes in performance. Comparisons of power consumption, magnetic flux density, signal-to-noise ratio, and detection range showed a 2X increase in performance of rejecting nearby benign metallic objects performance with a 25-40% loss in power efficiency to generate a magnetic field. Through these findings, metal detection designers can optimize their systems for the local metallic environment while simultaneously improving detection performance with minimal additional hardware and power requirements to advance large-scale free-flowing metal detection for crowds.