For conversations, "to butt in/into" is common.
I hate to butt in, but I heard you mention Porto Seguro, and I....
Frank is always butting into private conversations.
(The idea is that the person is hitting with his head as a goat or bull might do.)
"To interrupt" is more formal.
You can walk in halfway through the movie, in the middle of the movie...
You can crash a party.
Forgive me for crashing the party. I needed to talk to Susan and I neglected to call first.