MetaSound is one of the most powerful additions to Unreal Engine 5. They allow sound designers and composers to create procedural and responsive audio. Using some few basic nodes, you can create a lot of different behaviors; from simple randomizable sounds up to very complex audio and music structures.
For a quick start, you can take a look at Unreal Engine's official MetaSound documentation. There you'll find an introduction to this subject, however you'll find that a lot of times you might want to do some simple stuff and it's hard to find either docs or videos about the subject. I had to deal a lot with them and now I think I've finally got a good understanding of all the system and nodes. I've created this section as a tutorial so you can start from scratch and learn quickly using basic examples usually required in video games.