Now that magnets can attract iron, can they also attract other metals? Our ancestors made many attempts and found that magnets can not only attract metals such as gold, silver, copper, etc., but also cannot attract bricks and other items. In the Western Han Dynasty, people had realized that magnets could only attract iron, but not other objects. When two magnets are brought close to each other, sometimes they attract each other and sometimes they repel each other. It is known that magnets have two poles, one called N pole and one called S pole. Same-sex poles are mutually exclusive, and opposite-sex poles are attracted to each other. At that time, people did not know this truth, but they were still aware of this phenomenon.

In the Western Han Dynasty, there was an alchemist named Luanda, who used this property of magnets to make two pawn-like things. By adjusting the mutual position of the polarities of the two pawns, sometimes the two pawns attracted each other and sometimes repelled each other. Luan Da called it "fighting chess." He dedicated this novelty to Emperor Hanwu and demonstrated it on the spot. Emperor Han Wu was so surprised that Longxin was so happy that he was named Luan "General of Five Benefits". Luan Da made use of the nature of magnets to make novel things to fool the Emperor Han Wu.

The earth is also a large magnet. Its two poles are close to the geographic south pole and the geographic north pole, respectively. Therefore, when the magnets on the surface of the earth can rotate freely, the magnets are repelled by the same sex, and the nature of the opposite sex attracts north and south. The truth is not clear to the ancients, but they are very clear about such phenomena.

Magnets can be divided into "permanent magnets" and "non-permanent magnets". Permanent magnets can be natural products, also known as natural magnets, or they can be manufactured by man. Non-permanent magnets only have magnetism under certain conditions, and are usually produced in the form of electromagnets, that is, the current is used to strengthen their magnetic field.