Is a metal active in a primary cell, and must the electrodes be metal?

Not necessarily.

In a primary cell, a metal with strong activity is usually used as the negative electrode, while a metal with weak activity (or a non-metal) is used as the positive electrode. But there are exceptions, as shown in the following figure:

Mg does not react with NaOH solution, and Al can react with NaOH solution to lose electrons, so Al is the negative pole;

Fe passivation in concentrated nitric acid, Cu and concentrated HNO3 reaction to lose electrons as the negative pole

Primary cell is a device that converts chemical energy into electrical energy, and the nature of the reaction is redox reaction.

Conditions for the formation of a primary cell:

(1) two electrodes of different reactivity.

(2) The electrodes are inserted into the electrolyte solution.

(3) Connect the electrodes with wires to form a closed circuit.

(4) The ability to carry out spontaneous redox reactions.