Achieving comprehensive ecological balance in a construction organization necessitates adherence to sustainability and other circular economy concepts. Geopolymers are an environmentally friendly alternative to conventional concrete since they use derivatives from coal-based industries and abundant natural precursors. Lightweight geopolymer concrete with LECA and a calcium-free composition is an excellent ingredient for structural, thermal, and acoustic insulation. LECA is a shaped, lightweight aggregate that is used in varied amounts to replace natural coarse aggregate. This substitution significantly reduces the density and thermal conductivity of geopolymer concrete, although prior research has been conducted on Metakaolin blended Fly ash and Fly ash blended Metakaolin using various polymerization reagents. In this investigation, fly ash (class F) was combined with metakaolin in sodium silicate and sodium hydroxide reagents. The microstructure of Lightweight Aggregate Geopolymer Concrete substituted with LECA in various proportions was investigated using SEM analysis, as well as rheological characteristics, density, compressive strength, tensile strength, flexural strength, impact resistance, modulus of elasticity, and stress strain curve. The results were compared to conventional concrete and normal weight geopolymer concrete. Geopolymer combination proportions and Mix Design are also investigated. The property inquiry and cure periods range from 28–360 days. The results showed that LECA in the matrix increased workability, lowered density, decreased mechanical and durability strengths and improved thermal insulation and fire resistance. Additionally, up to 40% LECA replacement meets the required standard for structural applications and higher levels of LECA inclusion can be used for lightweight blocks and wall panels.