this question is from the Ukraine megathread but I thought I'd put it here in case it gets buried in the megathread since its an important question @ass (who I guess it won't let me tag)

I want to understand NATO aggression in a more concrete way

What happens to Russia if Ukraine joins NATO, putting NATO on Russia’s border? What are the possible military, economic, social, political consequences?

Also, related, what would motivate Ukraine to want to join NATO? What do they get in the bargain?