Multifunctional 3D microstructures have been extensively investigated for the development of new classes of electronic and optical devices. Here, functionalized, free-standing, hollow, 3D, dielectric (150 nm thick aluminum oxide) microcontainers with metal patterning on their surfaces are realized by an evolved self-assembly approach. To functionalize the 3D structure and use it as a device, metal patterns, arrays of split-ring resonators (SRRs) acting as metamaterials, are defined on the surface of the 3D dielectric microcontainers. The SRRs on all six facets of a given microcube show a resonant behavior in terahertz regimes. Since desired metal and semiconductor patterns can be incorporated onto surfaces of 3D dielectric microstructures, this self-assembly process can be harnessed in developing next-generation microdevices utilizing the numerous advantages of 3D configurations.