Custom games matchmaking?

I just got my copy, but I don’t have an Xbox One quite yet. How do custom games work in Halo 5? Is there any matchmaking or hosting public lobby’s or games? In previous Halo games, the only way to play on custom maps or with custom game types was to manually invite each player (which means either your friends, or browse for people to invite) but there was no way to host a game for anyone to join. I really love and look forward to Forging maps, but am always wishing I could play big games on them.