Sometimes, we might observe a very common phenomena which happens when we boil water in a utensil. After getting heated for a while, the lid covering the utensil jumps off in air. Now what makes the lid jump off? There must be some energy behind it. This mechanical energy which makes the lid jump off in air, comes from the heat energy of the flame of the gas stove.
This example supports the fact that heat is a form of energy which can be converted to its other forms too.
Heat energy can be converted into mechanical energy, electrical energy, etc.