Justin Bieber showed how much of a smooth operator he is by pulling a move on Hailey Baldwin that also signals just how serious they are this time around.

The couple hung out in Brooklyn Sunday where they looked so in love they were completely oblivious to anything going on around them. Besides your standard making out, Justin also hit Hailey with the ol' forehead kiss. Makes 'em melt every time.

Sucking face in public ... it's become their thing.

They've been practically inseparable since rekindling things last month ... although, Justin did take a brief break on Friday when he flew West for a special delivery.