If the outer glass on your microwave is damaged, it's essential to take care when using the appliance. While the inner workings of the microwave are designed to be safe, the outer glass can pose a danger if it's cracked or chipped. When using a microwave with damaged outer glass, be on the lookout for signs of further damage, such as sparking or arcing. If you find any damage to the outer glass, stop using the microwave and call a technician for repair. In most cases, it's best to avoid using a microwave without outer glass until it can be fixed by a professional.