It's a functional language with all the usual bits that entails, so writing pure code is right in its wheelhouse. It's a pragmatic, dynamic language, so very much an easy on-ramp to functional programming. The testing library (ExUnit) is good too, so with pattern matching testing is a joy.
Where it really stands out is the runtime model. You can spin up as many GenServers as you want to hold and update state - they're like goroutines so they're very cheap and you can have thousands. They're a great way to handle state as you just handle incoming messages one after the other and change your state appropriately. Then you arrange them with supervisors so that if one does something unexpected it's restarted and going again.
Where it really stands out is the runtime model. You can spin up as many GenServers as you want to hold and update state - they're like goroutines so they're very cheap and you can have thousands. They're a great way to handle state as you just handle incoming messages one after the other and change your state appropriately. Then you arrange them with supervisors so that if one does something unexpected it's restarted and going again.