Dynamical control of the constitutive properties of a light beam is important for many applications in photonics and is achieved with spatial light modulators (SLMs). Performances of the current demonstrations, such as liquid-crystal or micro-electrical mechanical SLMs, are typically limited by low (∼kHz) switching speeds. Here, we report a high-speed SLM based on the electro-optic (EO) polymer and silicon hybrid metasurface. The specially configured metasurface can not only support a high-Q resonance and large “optical–electrical” overlap factor, but also overcome the challenge of polarization dependence in traditional EO modulators. Combined with the high EO coefficient of the polymer, a 400 MHz modulation with an RF driving source of 15 dBm has been observed in the proof-of-concept device near the wavelength of 1310 nm. The device with the desired merits of high speed, high efficiency, and micrometer size may provide new opportunities for high-speed smart-pixel imaging, free-space communication, and more.