Video narration
If two metals in one liquid produce no voltage, you have found the problem: unlike a torch battery, there are no separated terminals and no complete circuit. Build a Daniell cell with two half-cells. Place zinc in zinc sulfate solution and copper in copper sulfate solution. Keep them separate. Connect the electrodes with a wire or voltmeter, then join the solutions with a salt bridge. That is the key: two metals alone are not a cell. The wire carries electrons; the salt bridge carries ions and keeps the solutions balanced. Zinc releases electrons, so they travel through the meter from zinc to copper. Zinc is oxidized at the anode, the electron-releasing electrode; copper is the cathode, where copper ions receive them. The meter shows a voltage, depending on the conditions. Remember: zinc supplies the electrons, copper receives them, and the salt bridge keeps charge balanced.