Mobile robots have advanced significantly in agility, intelligence, and efficiency, yet their endurance remains limited by onboard power supplies. Current solutions restrict robots to areas near electrical grids or require heavy batteries for extended range, while energy refueling in remote locations presents significant challenges.We propose a bio-inspired approach: enabling robots to "digest" energy-dense metals for power generation, similar to how animals process food for energy. We focus on aluminum-air batteries, which function as miniature chemical plants converting aluminum into electricity. This technology offers three key advantages: exceptional energy density compared to lithium batteries, simple anode replacement for rapid refueling, and readily available fuel sources from everyday aluminum materials. Through four interconnected studies, we investigate the implementation of aluminum-air batteries in robotics. First, we quantify the energy gap between mobile robots and biological systems, establishing benchmarks for bio-equivalent performance. Second, we implement customized metal-air batteries for an Arduino robot, demonstrating continuous operation through metal oxidation while addressing challenges of byproduct accumulation and water management. Third, we develop a highly stretchable metal-air battery using sliding electrodes, achieving 10-fold improvements in areal capacity and power over existing designs. Finally, we develop a highly efficient actuator based on cascading dominoes to realize solion waves, contributing to the overall development of soft metallivore robots. Our key innovation lies in optimizing interface contacts, particularly between metal anodes and hydrogel electrolytes in metal-air batteries, leading to improved capacity and stretchability. This optimization extends to the mechanical domain, enabling efficient solion wave propagation. Together, these developments demonstrate a pathway toward extended robot operation in remote and complex environments.