Here we present the first full-cell battery device that is developed entirely from scrap metals of brass and steel – two of the most commonly used and discarded metals. A room temperature chemical process is developed to convert brass and steel into functional electrodes for rechargeable energy storage that transforms these multicomponent alloys into redox-active iron-oxide and copper-oxide materials. The resulting steel-brass battery exhibits cell voltages up to 1.8 V, energy density up to 20 Wh/kg, power density up to 20 kW/kg, and stable cycling over 5000 cycles in alkaline electrolytes. Further, we show the versatility of this technique to enable processing of steel and brass materials of different shapes, sizes, and purity, such as screws and shavings, to produce functional battery components. The simplicity of this approach, building from commonly available chemicals enables a simple pathway to the local recovery, processing, and assembly of storage systems based on materials that would otherwise be discarded.