Red rising Trilogy by Pierce Brown is the first that comes to mind, it follows the young male protagonist in admittedly a darker and more mature story, but the action and story keep you very engaged. Fantastic character work as well in my opinion.

Another scifi series that's very fun but not necessarily an 18yo male is the Murderbot Diaries by Martha Wells. I've only read the first novella, but I'm constantly on the lookout for the rest I enjoyed it that much.