In this study, a planar multilayer metamaterial absorber capable of optical sensing across an ultra-broadband spectrum was designed and numerically analyzed using the finite element method implemented in the simulation software COMSOL Multiphysics (V6.0). The absorber consists of alternating metal–dielectric layers, with SiO2 serving as the scattering medium to enhance electromagnetic coupling and impedance matching. A six-layer planar structure composed of V, Ge, Bi, and Co was first developed, achieving an average absorptivity of 94.56% within the 500–3160 nm wavelength range, though a slight absorption dip was observed between 400–500 nm. By introducing additional SiO2 and Co layers to form an eight-layer configuration, the absorption bandwidth was broadened to 400–3700 nm with an average absorptivity of 93.69%. Furthermore, replacing Co with Ti extended the spectral response to 400–4000 nm, demonstrating enhanced optical adaptability. These findings indicate a design trade-off between absorption efficiency and bandwidth coverage, offering valuable insights for the development of high-performance optoelectronic and sensing devices based on planar metamaterial architectures.