How about dubbing for fight sequences? Do the actors dub for the fight sequences as well or is any other method used like using the original set audio along with the background music?
It can be done during post-production, as part of the Additional Dialogue Recording (ADR) process
Matthew Wood, from the Star Wars clip below, talks about how:
...the sounds [recorded on set] don't sound realistic. I mean obviously when they're fighting with those light Sabres it's the sound of a stick hitting, so you really hear a plastic or a wood hit, you know, and they might be walking on wood, so they're not on stone and all those sounds come through to the microphone and so when they're breathing, talking you get all these clicks and clacks.
So we have to go back [during post-production] and the actor has to recreate that energy again and hopefully you're getting performances that were better than they recorded on the set.
If you're talking about the latter, then Hugh Jackamn posted this excellent video of ADR recording for Logan:
See also Hayden Christensen doing a similar recording session for Revenge of the Sith: