Since steel and aluminum cans are accepted for recycling, you may assume tossing an old screw or worn out pot into the curbside bin wouldn't be a problem. However, metals not shaped like cans can easily get into other streams (I.e. paper, glass) and then contaminate that load because the sorting facility wasn't designed to handle irregularly shaped metals. You can take your scrap metals to local facilities, or consider donation if the item you are trying to dispose of is still in usable condition. If you have metal screw top caps, you can put these into a can and crush the top of the can, containing the metal.
Check out our Reuse and Recycling Search Tool to find locations for where to recycle or donate your item in question.