Users of the Android Facebook Messenger app have been able to change the UI from Light Mode to Dark Mode since 2019. Dark Mode converts the usual black print on white background to white print on black background and it can prevent the user’s eyes (or those belonging to a innocent bystander) from melting in the dark of night or in a dark room. In addition, Dark Mode can extend battery life a tad on phones sporting an OLED panel.
Update will allow the Android version of Facebook Messenger to follow the user’s system setting for Dark Mode
We should point out that this feature is already available on the iOS version of the app. The system setting is for those who like to switch back and forth between Light Mode and Dark Mode so that a user can switch from Light Mode to Dark Mode and back without having to worry about switching the Facebook Messenger separately each time.