Mylar balloons are shiny, metallic balloons made from a type of plastic called polyester. They are often used for celebrations like birthdays and holidays because they can be printed with colorful designs and messages. Mylar balloons are known for their ability to hold helium longer than traditional latex balloons, making them a popular choice for events. These balloons come in various shapes and sizes, including hearts, stars, and characters from popular culture. Mylar balloons are also reusable; they can be deflated and stored for future use. However, they should be disposed of properly to avoid environmental harm, as they do not decompose easily.