Bronze is available for 1.21.1 on both Neoforge and Fabric, and a PR has been submitted for 1.21.5. See it on Modrinth
I have tried several mods that let you make equipment out of various materials—copper, amethyst, obsidian, or others, but Bronze is by far my favorite.
Iron is often in short supply in the early game. I need to build hoppers, cauldrons, buckets, and then the tech mods I play with often need a lot of. Bronze fills in the gap between stone tools and iron (or diamond) tools. Bronze adds a new ore, tin, which you can combine with copper to make bronze. You can combine it in your inventory 2x2 crafting square, so it can also help to save space while you’re out mining tons of copper. 3 copper and 1 tin combine to become one bronze.
Bronze adds the full suite of tools and fully trimmable armor. It’s not quite as good as iron, but it’s close. With how common copper and tin are, replacing broken gear is never a problem.
In addition to the full suite of weapons, tools, and armor (as well as some decorative blocks), bronze also adds a new tool: the sickle. It’s great for mowing down weeds, and for harvesting and replanting crops.
One more thing Bronze has going for it is that it’s fully compatible with Basic Weapons which adds a handful of new weapons like a spear and dagger that add a new dynamic to combat and are fun to play with.