The best materials for butt plugs are body-safe options like silicone, stainless steel, glass, or medical-grade plastic. Silicone is popular because it's soft, flexible, and non-porous, making it easy to clean and comfortable for extended wear. Stainless steel and glass plugs provide a firmer, heavier feel and can be heated or cooled for temperature play. Avoid porous materials like rubber or jelly, as they can harbor bacteria and are harder to clean. Always check that the material is hypoallergenic and free from harmful chemicals.