Along with a string of new features across several areas of Android, Google is at last turning on (E2EE) for everyone in the Messages app. Beta testers have been able to use E2EE messaging since November.
E2EE in Messages is only available in one-on-one conversations for the time being, not group chats. Both participants need to have RCS chat features enabled to use it. You'll know if a message you're about to send will be encrypted if you see a lock icon on the send button. It'll then be harder for prying eyes to snoop on your messages.
The E2EE feature is rolling out this week as past of an Android update, alongside the likes of starred (or pinned) messages and availability of an earthquake alert system in more countries. The update also includes new emoji, Assistant, Android Auto and Voice Access features.