Look, we all know you've seen that Baldur's Gate 3 video. The one where they explicitly tell you that you can romance a bear if you want to. Well, in terms of Druids in the game, Halsin is the guy that you want, and he's a few hours into the game, so you'll have to strap in to really get to that big furry guy.
You'll first hear the name Halsin when you reach a Druid encampment early in the story. He's been taken captive by Goblins and it's up to you to get him back, which involves either sneaking your way into a Goblin Camp, persuading them that you're a friend, or killing them all. You can really choose to do it any way that you want to do it, but keep in mind that if you start a fight you'll probably have to fight through about a hundred Goblins.
Once you get into the stronghold, you can free Halsin, complete his request, and take him back with you to the Druid Stronghold where he'll wait for you until you ask him to join your camp.
You can't take Halsin with you on quests to start with, though, and he'll simply stay in your camp (assuming you side with the Druid Encampment in the battle that Minathra wants to take over). You can talk with him in your camp and flirt with him, which will start the process of trying to romance the bear.
Recruiting Halsin In Act 2
During Act 2, Halsin will ask you to help him lift the shadow curse that is afflicting the land, and if you help him out successfully then he tells you that he'd be happy to join you in your battle against the Absolute. From here, as long as you lift the Shadow Curse, he'll be able to join your party for the rest of the game! Don't fret if he leaves and you still want a Druid, though, as there's another Druid in Act 2 of Baldur's Gate 3 that will willingly join your party.