A key part of Horizon Forbidden West combat is sneaking up to machines to silent strike, override them, or in some cases avoid them entirely. As you explore the open world you will come across machines that are too tough to deal with. There are even some quests that you can avoid killing the machines in your path by sneaking past.
The best way to sneak past machines is to hide in the long grass and use the focus to mark their patrol path. This will tell your exactly where the machine will walk. Once you know the path of the machine, you can throw rocks by pressing down on the D Pad to draw its attention away from you so you can sneak between long grass patches.
How to stealth past machines?
There are other methods to stealth past machines as you level up and gain access to new skills, such as the Infiltrator skill tree. This skill tree includes buffs to your stealth capabilities like low profile and quiet movement. The Valor Surge, Stealth Stalker will allow Aloy to activate a cloaking device similar to the Stalker machines to decrease your visibility to enemies.
For more on Horizon Forbidden West guides, check out How to cook food in Horizon Forbidden West, and is it worth it? and What is Azure Bloom used for in Horizon Forbidden West?