Electrode materials for EDM should have high electrical and thermal conductivity to reduce heat generation and tool wear. Commonly used materials include graphite, copper, brass, and tellurium copper. Graphite electrodes are inexpensive but wear quickly, while copper provides better finishes and conductivity at a higher cost. The material removal rate in EDM depends on factors like the workpiece material, electrode material, pulse conditions, and dielectric fluid, with higher currents and longer pulse times increasing the removal rate but also the surface roughness.