I love rusty old things that are lying around in all sort of places.  These horse shoes are on this rack at a farm that I sometimes pass on my walks. 

Think about what details you want to show.  I took this at a wide aperture (a low f number) so that I could get the details on the first horse shoe. I got in close to see the detail and reminded myself to consider  the length of focus of my lens.

What rusty thing can you find today to show the details?