Looper is the sort of film that covers most every aspect possible when it comes to the variations of ideas relating to Free Will and Determinism. Fate also place a strong central point as well as the "Loop" in looper is created as a fated event it is revealed, the main character whose name is Joe, has a choice in stopping. The whole mechanics behind the movie take a bit to unpack and understand, but once these things are laid out, the philosophical underpinnings and how the arguments of free will vs determinism become very relevant.
Looper is based around the concept that sometime in the near future, about 30 years from the year 2044, time travel will be invented and outlawed by every nation on the planet. The only people who will have access to this technology are large scale criminal organizations who operate them in secret. The "Loopers" like the main character Joe, are contracted assassins from the past. A single man was sent back from the future to organize and setup the "Looper" network. In doing so, he recruited a bunch of younger men to in a sense "take out the futures trash." Because of other tech that has been invented in the future, something about body tracking, it's never really elaborated as to why, these criminal organizations send people they want "gone" to the past. So people that need to be disappeared for whatever reason are sent back to the past to appear at a very specific place at a very specific time. The looper then proceeds to take out a blunderbuss and shoot whatever bound person appears before them. Their faces are covered as well, so they cannot say with certainty as to who it is they shot. They collect payments in silver from the corpses and dispose of the bodies.
The reason that Loopers are called what they are is because of a specific proviso they have in their contracts. Eventually they will be forced to "close their loop" so their involvement in the organization will have effectively been nonexistent.