The main focus for combat in Horizon: Forbidden West will be against the various Machines you encounter during the journey. There is a total of 43 Machines in the game, although a few of them are either not fought or only appear during select missions. The rest, however, can be found in the open world, allowing you to do battle with them and harvest all of the goodies.
One of the biggest things you can do with any Machine is scan them using the R3 button , which is simply done by pushing in the right analog stick and holding it until a target reticule appears on your screen. Hover that reticule over a Machine to scan it, which will take a second or so if you’ve previously scanned it and a few more seconds if it’s a brand new scan. You should get accustomed to scanning pretty much anything and everything in the game, but you will want to do this with Machines every time you come across a new one. Upon doing so, a small window pops up that shows relevant information on that Machine, including strengths and weaknesses.
If you press the left and right buttons on the D-Pad, then you will be able to see the various parts you can target on the Machine. While also in scan mode, you will be able to use the R2 button to mark the Machine, R1 to highlight its tracks and follow its movements (when not alerted), and for the individual parts, you can press Triangle to highlight that part when fighting so you can more easily target it. If you scan all of the Machines (variants not needed), then you will unlock the All Machine Types Scanned trophy. All information on the Machines, once you’ve scanned them, will be in the Machine Catalogue portion of your Notebook.
Both the Specter and Specter Prime machines are missable, as they are only available during select missions. If you happen to miss scanning them during those missions, then you will not be able to unlock that trophy on that current save file.
As you explore the game’s world, you will see that certain Machines can be found at specific spots on the world map. These are Machine Sites and the specific Machine will almost always be found there, making it easier to locate one when you need them. Of course, you can also find Machines outside of those sites, so you aren’t limited to those, but they make things a lot easier without blindly searching or going from memory. One such example is that you will find a lot of the Recon/Combat class of Machines with some of the lesser ones. Grazer sites in the Plainsong area will almost always have some other Machine with them, like a Clawstrider.
If you take a glance at the Machine Catalogue, you will notice that some of the Machines have a listing for Variants. These are largely the same Machines as the base ones, but will usually have something different about them. This can be as minor as a Machine having an Acid Canister on it or a Fire Canister, while some Machines (like the Burrower) will have a different part altogether, which can grant it a new function. While you don’t need to scan each Variant for the above trophy, it’s a good idea to do that so it gets catalogued in your Notebook. One more Variant that most machines will have is called an Apex variant. These are stronger than their normal versions, with some new loot that cannot be obtained elsewhere, and some may even have new moves.