Identifying metal post next to a house
That looks like a cut off T-post (fence post), and IMHO it is a significant hazard, especially to kids and dogs. If a dog steps on it wrong it could slash a foot to the bone.

https://www.lowes.com/pd/T-Post-Post/4758566

If you have a high lift jack or T-post puller you could probably wrap a chain around the post and pull it out. Otherwise just dig it out. Usually these are driven it no more than 1 ft or 18". Usually they have a stabilizing plate parallel to the top of the T cross section.