Absorbers are indispensable tools in microwave technology, employed for preventing radiation leakage and interference from devices, radar cross-section reduction in defence aircraft, mitigating cavity resonances in enclosed systems, and so on. Metamaterial-based absorbers, with their compact design and user-defined frequency characteristics, are a better replacement for traditional absorbers, which are bulky and often limited in frequency response. However, the reliance on commercial substrates like FR-4 to design metamaterial absorbers puts constraints on unit-cell engineering and practical implementation due to their fixed dielectric and mechanical properties. Developing custom substrates for metamaterial absorbers provides a holistic way to design these electromagnetic structures by providing choice over dielectric constant, thickness, and flexibility. This research involves finding suitable substrates for microwave metamaterial absorbers focusing on miniaturization and conformal applications. The first part of my research addressed a solution to the problem of reducing the dimensions of the metamaterial absorber by developing a high-permittivity ceramic substrate. In the next part, I fabricated flexible metamaterial absorbers using polymer nanocomposites as substrates with varying dielectric constants. The third part delves into enhancing the operational bandwidth of the flexible absorbers through a synergetic approach involving material engineering and topological optimization of the resonating structures. In this talk, I will explain how these custom-engineered substrates lead to leveraging the properties of metamaterial absorbers, which can help realize practical and efficient microwave devices.