Storm doors without glass
What you are looking for, then, is a security door.  These are essentially storm doors with metal bars that make entry more difficult.  They come in a variety of styles and prices.  If you need the "storm" protection as well, you can get some that include glass or plastic, or you can mount a plastic sheet to the inside.

It will look better than a solid non-transparent metal door, and provide significantly more security than any storm door, without a significant increase in cost.

Also, keep in mind that storm and security doors are relatively simple.  If you cannot find what you want, you can buy the door hardware (hinge, latch, gas spring return), sheet metal, and metal tubing to create your own.  A hacksaw, drill, and screws or rivets, plus metal paint, is all you need. It won't be as secure as a security door, though, unless you buy security door hardware. But if all you're looking for is a storm door without glass, this would provide the same level of security.

Also worth considering is buying a storm door with a plastic window.  Some additional clips, or replacing the window with plastic, will provide slightly more security while maintaining the look of a traditional storm door.