Before iron didn't have a magnetic field, the electrons inside the atom were spinning around in a chaotic order and spinning around the nucleus. Because the electrons are moving in different directions, the magnetic effects cancel each other out inside. When they encounter a magnet, the atoms within it line up, forming a self-magnetizing zone called a domain, which strengthens their magnetism and attracts them to the magnet. Magnet in the process of absorbing iron is the magnetization of iron process magnetized iron and magnet between different polarity attraction, iron and magnet will be absorbed together, that is, we say magnetic.
Copper is an diamagnetic substance. When it's in a magnetic field, it creates a repulsive force. Copper atoms have a magnetic moment of zero, which makes it difficult to magnetize even if the external magnetic field is strengthened. Similarly, aluminum is not attracted. Aluminum is a paramagnetic material, basically has no magnetic field inside, but it will produce a certain magnetic field when it meets a magnet, but the magnetic field is very weak, not even ten millionths of iron, so aluminum will not.
