when does it make sense to use a message queue

Hey everyone, I've noticed message queues popping up a lot in system designs lately. They seem great for decoupling services and tackling background tasks. But I'm wondering, when do you guys find message queues really shine? Is it just for async stuff, or are there other big wins, like fault tolerance or load balancing, that make them a must-have for some setups? Also, what are your favorite message queue systems, and what makes you pick them?