Before the coming of the European, the American Indians (North America) did not use metals for weapons (except, it is said, the Intuits worked meterorites).
They are known to have made things from copper.
As I understand it, Indians never did forge things from steel (requires too hot of a temperature anyway; and stainless wasn't invented until 1926).
My question is: once they learned of metals, did they forge things, themselves out of iron?
Not discouraging further answers, but this section of our FAQ on native American metalworking may be of some interest to you.
Not that I am aware of. In fact most of the histories of Native Americans I have read expressed frustration by Native Americans on their dependence on European settlers for metal goods such as knives and muskets.
did they forge things, themselves out of iron?
Indeed they did. As far as I know, their forging was restricted to cold forging, and often as much or more of the shaping was done by grinding as by forging (the combination of grinding and forging is usual, but often the grinding is only for the final shaping and finishing of the surface). Since iron is quite resistant to being shaped by hammering (i.e., forging) at room temperature, cold forged objects tend to be small and often thin. Also, cold forging doesn't let you do forge-welding, so the final objects made can't be as complex.
Sometimes the forging step was largely just flattening the piece of scrap iron being used, to produce a flat sheet which is then ground to shape.
Pre-Columbian forging of iron was restricted to meteoric and telluric (i.e., native iron of terrestrial origin) iron. Later, iron was traded in advance of European contact, and on the coasts, iron was recovered from shipwrecks.
Some examples:
Iron harpoon head: https://www.amnh.org/exhibitions/permanent-exhibitions/northwest-coast-hall/tlingit/tlingit-collection/fishing-and-hunting/spearheads-of-slate-bone-and-iron
Arrowheads: https://www.nps.gov/fous/learn/historyculture/arrows-guns-and-buffalo.htm
Iron-bladed knife, possibly native-forged rather than a trade blade: https://i.pinimg.com/564x/60/f5/3f/60f53f479b3d571cf84ea06a18a50500.jpg
Arrowheads and lance head: https://texasbeyondhistory.net/st-plains/images/he8.html