Hey, he has a legitimate purpose (pest control is a valid and legal reason to keep a loaded REAL firearm around; look it up) and is asking a valid question. No need for flames here.
To answer your question alexkolb, airsoft would not be right for you. The guns are usually much lower in power than a typical BB or pellet rifle, and as mentioned above shoot plastic pellets. Steel and aluminum BBs are available but they are hard to come across and will not get any kind of decent velocity from an airsoft gun. Your best option is to purchase a Gamo air rifle that will attain 495+ fps with a .177 lead pellet, which will punch cans more easily and be far better suited to pest control. Hope this helps.