Reactive metals are stored in oil to protect them from exposure to oxygen and moisture, which can cause the metals to corrode. Oil acts as a barrier between the metal and the atmosphere, preventing the metal from coming into contact with oxygen and moisture. This helps to preserve the metal and prevent it from deteriorating.

Some reactive metals, such as sodium and potassium, are so reactive that they can ignite in air. Storing these metals in oil helps to prevent them from coming into contact with air, which could cause a fire.

Oil also helps to protect reactive metals from mechanical damage. When reactive metals are stored in oil, they are less likely to be scratched or dented, which can weaken the metal and make it more susceptible to corrosion.

In addition to protecting reactive metals from corrosion and mechanical damage, oil can also help to improve the thermal conductivity of the metals. This means that heat can be transferred more easily through the metal, which can be beneficial in some applications.