Melted butter is a type of butter that has been heated until it becomes liquid. This process typically occurs by placing a stick or block of butter in a microwave, saucepan over low heat, or even just leaving it out at room temperature for an extended period of time. Once melted, the butter can be used as a cooking ingredient, such as in sautéing vegetables or adding flavor to dishes like popcorn or roasted vegetables. It is also commonly used as a condiment, drizzled over foods like bread, pasta, or potatoes.