Fire is not a solid, a liquid or a gas because it is not a state of matter. Instead, it is a process of rapid oxidation in which heat and light are released. Fire can be used for both creative and destructive purposes.
Fire is an important process that plays major roles in ecological systems and human civilization. It removes debris from ecosystems, stimulates growth and is necessary to some plants for reproduction. Human beings use it to cook, warm themselves, generate light and shape and create other things. On the negative side, fire can destroy the nitrogen content of soil, release pollution into the atmosphere, contribute to soil erosion by removing protective vegetation and destroy human and animal habitations.