If you want to build any cool stuff in Atlas, then you will need to learn how to find raw material and turn them into ingots, such as copper ingots, iron ingots, iridium ingots, silver ingots, tin ingots, and cobalt ingots.
The first step is to get some skill points. You will need the Metallurgy skill found in the Construction & Mercantilism skill tree first. This skill cost two skills points. You will need to get two addition skills in the same skill tree as well; Secrets of Building and Chemicals & Tanning skills.
With these three skills in place you will be able to build a forge, which is essential when you want to make ores into ingots. Each different type of ingot requires a different raw material to create, and many of them simply need metal ores + coal, which should be pretty straightforward to get your hands on. Ores are found all over the map randomly, while coal can be crafted by burning wood.
If you plan on making a Cannon, then any ingot created at the forge will count as an alloy. So just use the ones you currently have most of, or don't need for anything else. You need a total of 28 alloys, so it might take a while of farming to get all the materials you need tough.