Vanadium dioxide (VO2) is a remarkable phase-change material whose temperature-driven insulator-to-metal transition unlocks powerful tunability in the THz regime. Here, we present a VO2-based metasurface that not only achieves over 90% absorption efficiency across a broad 1.27–2.64 THz range when in its metallic phase, but also transitions into a nearly perfect reflector (0.1–4 THz) in its dielectric phase. This striking dual functionality leverages the unique conductivity variation of VO2 with temperature and is realized through a metasurface on a thin SiO2 spacer backed by a gold layer. Notably, our design maintains insensitivity to both polarizations and incidence angle—crucial characteristics for practical THz applications—while offering a robust, wideband response. Through systematic analysis, we elucidate the physical mechanisms governing the high absorption and reflection, and demonstrate how key …