The properties of porous and lightweight ceramic foam that can be cured at room temperature using metakaolin-based geopolymers were studied. A geopolymer slurry was prepared using metakaolin and a potassium-based alkaline medium at room temperature, and the obtained viscous paste was expanded via gaseous methods, by means of the decomposition of peroxide at room temperature. Therefore, geopolymer (GP) foam developed in this study through multivariate geopolymer, foaming agents, and surfactants can be cured at room temperature (within 5 days) without a separate heat treatment process. The homogeneous micropores were obtained through the stabilization of the interface between geopolymer slurry and oxygen gas bubbles generated through the base-catalyzed decomposition of hydrogen peroxide. The porosity was confirmed to be 29% and 54% before and after using sodium dodecyl sulfate (SDS). The compressive strengths and densities were 1.57 MPa and 0.75 g/cm³ for GP foam without SDS, and 3.63 MPa and 0.48 g/cm³ for GP foam with SDS. Through the mercury intrusion porosimetry analysis, the pores were further refined from 100 µm to 30 µm when SDS was used, and at the same time, the variation of pore size was minimized, so that a relatively uniform pore size was maintained. In addition, the thermal conductivity is 0.0803 W/m·K and the pore size is 33.2 $\mathsf{\mu }\mathrm{m}$, which is smaller in pore diameter than the geopolymer containing only hydrogen peroxide. As a result, although the hydrogen peroxide alone sample has excellent thermal conductivity, the use of a surfactant is recommended for fine micropore size control. While reducing the non-uniform distribution of pores and the size of micropores generated through the direct foaming method as an inorganic binder, the possibility of an insulation finish was also confirmed by reducing the weight.