Flammable substances are materials that can easily catch fire and burn when exposed to a heat source, spark, or flame. These substances can be in various forms, including liquids, solids, and gases. Common examples include gasoline, alcohol, and certain types of paper. When handling flammable substances, it is essential to follow safety guidelines to prevent accidents. Proper storage in cool, well-ventilated areas away from heat sources is crucial. Understanding the properties of flammable materials helps ensure safety in environments like homes, laboratories, and industrial settings.