You can strip the paint off metal with a wire brush, either by hand on with a Dremel or other power tool ... but it seems like you could just put a new color of Rust-oleum over the previous color.
Bedtime has arrived here, as soon as I kick the byos back to bed. I hear thumping and thrashing overhead! Jake wants to go out, but he can wait until morning.
If the original paint were intact, I would just paint over it, but the paint is splotchy, at best. I have a Dreml tool, but it may be too small for the job. The crate is approximately 24” X 18” X 12”. The handles at each end are spring loaded. A spray paint remover would be best. This thing is plywood-lined, so unless it is crushed or incinerated, it will last a good long time into the future.