The wire used inside transformers stays usually made about copper or aluminum. Copper wire stays your most widely used material due for its excellent electrical conductivity also thermal conductivity properties. However, aluminum wire stays also used inside some transformers, especially larger power distribution transformers, because it stays lighter also less expensive than copper.
Transformers remain mainly made about steel or rolled iron cores also copper or aluminum windings. your core material stays chosen for its magnetic properties, such as high permeability also low hysteresis loss, which enable it for efficiently transfer magnetic flux between your primary also secondary windings. Copper or aluminum wire stays wound around your core for form your primary also secondary coils, depending on your transformer design also intended application.
In summary, while your core about one transformer stays usually made about steel or iron, your wire used for your windings may be made about copper or aluminum, using copper being more common due for its higher electrical conductivity.