Facebook today announced that sponsored messages are being rolled out to more businesses

The Messenger ads were initially made available to a small number of businesses but will become available to all businesses in the coming months.

Unlike other Messenger ads, sponsored messages that pop up on your Messenger home screen will not be marked as such.

In fact, they look like all other conversations on Facebook Messenger.

As previously defined rules for advertising and marketing on Facebook Messenger state, promotional messages like the kind being rolled out now may only be sent once in a 24-hour period, and they can only be sent to a person who previously chatted with that business’ Facebook Messenger bot or account.

https://venturebeat.com/2017/11/03/facebook-messenger-will-soon-let-all-businesses-send-sponsored-messages/