That is next to impossible, but as you might already know, impossible does not exist.
Neither does unobtainium, but let's just use that name for things nobody can FDM print yet, like:
-Aluminum alloys like Dural, Ergal, etc.
-Metal alloys, various grades of
I know, I know, there are "metal" filaments, but are they metal enough?
Nope, they are plastic bonded metal powders, in the end your object is still plastic bonded, it is not that you can print all the parts of your diesel lawn mower engine, put it together and mow the lawn with it.
What I am looking at is the real deal, actually printing 100% metal fully functional objects like they do with Laser Sintehring machines (that cost a few neighborhoods of eyes and kidneys) but with an FDM machine that costs maybe, yes or no, in between, something, like 1 up to 3 minimum wage monthly salaries.
Yes there are a few people that "printed" metal actually using a MIG machine as extruder-nozzle, etc. but the result is more of something... artistic, rather than actually useful, unless you combine the printing part with a large 6 axis CNC milling machine that passe all your welded print with some milling bits to clean up the mess. Well that milling machine ain't no cheap, trust me.
Come up with solutions, if you thought of some, and if you did not, than think of something.