This research investigated the combination of acid functionalization and metal deposition on commercial activated carbon (AC) for the synthesis of electrodes for applications in supercapacitors. The effect of acid treatment and the deposition of metals, including nickel, copper, and cobalt on the electrochemical characteristics of the carbon material were assessed. The AC treatment with sulfuric acid resulted in a nearly twofold increase in surface area compared to the untreated AC, enhancing porosity and creating irregularities that improved the motion of ions and electrons, increasing the specific capacitance and energy density. Notably, we demonstrate that nickel deposition at only 2 wt% significantly improved specific capacitance (up to 59.58 F·g⁻¹), while preserving porosity and enhancing surface wettability. The adoption of a scalable, solvent-free, and low-energy technique for metal deposition on carbon structures presents promising opportunities for developing sustainable alternatives in energy storage technologies.