Fire is a very interesting poetry topic idea for a variety of reasons.
One reason is that fire can appear in settings in a spectrum of situations from good, through indifferent, to bad. Fire, for example, is found in fire places, grills, and campfires. It is also found in matches and lighters. Additionally, fire is seen in disasters, arson, and war. Because fire is found in this wide range of situations, it can be used in a variety of poems.
Another reason fire can make an interesting poetry topic idea is because it is dynamic. Fire moves, it changes color, in grows and shrinks. The fuel source of fire changes as it burns. The air around fire changes. This dynamism can make fire an interesting topic for poetry.
Fire also has a certain fundamental quality. Fire provides light and heat in a basic way that has been utilized for millennia. Fire can happen naturally. The fundamental quality of fire can be useful in poetry.