Poems, songs, and book are usually known to help with your listening skills and clearly, your fluency. With movies, it seems different to me for some reason. Movies have a lot of stuff going on with lots of movement and quick dialogue people need to comprehend quickly.
According to studies, how can watching movies help improve fluency and listening skills (if at all), assuming the movie is using the language I am learning.
What is beneficial is watching movies with subtitles in the original language of the movie. So if you're, let's say American, you will watch a French movie with the French subtitles, that is to say in your L2. Technology allows us to access DVDs with optional subtitles, including in the language of the movie. You can improve not only your listening skills but grammar and vocabulary as well. You need to watch the movie several times to get full benefit.
To get the full flavour of the movie first time you watch can be without subtitles. You might find you understand some of it because the pictures on the screen help you understand the spoken words. And the more you use this method the more you'll understand first time.
Second viewing activate the subtitles, obviously your eye will be drawn to the subtitles at least as much as to the picture, but don't forget, you've watched it once already. Reading helps you understand better what you hear, you can press the pause button if necessary, and even take notes if you are very keen. A good exercise is to spot the discrepancies between the spoken word and the subtitles.
Third time you watch again without subtitles and you'll be amazed at how much you understand then.
This is an excellent method for anyone studying on their own, outside any academic environment, but it can be done as a complement to any course. I've experienced myself with foreign languages in which I'm not fluent and on the professional side I've noticed students improving tremendously (listening skills, speaking skills and vocabulary) by watching movies in their spare time.
Lots of studies have highlighted the beneficial impact of watching movies in the L2. Those studies usually compare two groups of students: a group who have watched the movie in the L2 without subtitles, a second group who have watched the movie in the L2 with subtitles. First ones I've hit upon through google (lots more to be found):
Insight into Learners’ Perspectives on Watching Movies with L1 vs. L2 Subtitles:
This study suggests that learners may improve their spelling, word recognition ability, pronunciation of new words and words they have already acquired, their understanding of spoken language, and intonation when they watch movies with the L2 subtitles.
Movies in EFL classrooms: with or without subtitles:
The results showed that the English subtitle group performed better than the no subtitle group on the listening test.
I would like to add that I have found that, although not detrimental, watching foreign movies with subtitles in the L1 is not as effective as far as improving in the L2 is concerned.
Movies provide a distinct advantage over listening to music, because they provide visual cues to help discern meaning. When you watch someone speak, you don't just hear the words that are spoken, you also see the facial expressions, body language, and accompanying hand gestures used in conjunction with their dialog.
Here is an example from English of the importance of visual cues to deduct proper meaning:
When my oldest son [Linus Torvalds] was asked the same question: “Has he been approached by the NSA about backdoors?” he said “No”, but at the same time he nodded. Then he was sort of in the legal free. He had given the right answer, [but] everybody understood that the NSA had approached him. (Falvinge, 2013)
However, it is not just a free pass to say that movies will teach you another language. They have their disadvantages as well. Movies often use slang and slur their words when speaking or their sentences are not a uniform volume. Unless you have enough of a background to start to pick up on that, you can find yourself mimicking those bad patterns. This article lists more on these advantages and disadvantages in more detail.
One final note that is not mentioned in the article above. Movies are part of the cultural experience of the language you are trying to learn. When I talk about "There's no place like home", you instantly know that I am referring to The Wizard of Oz and I can convey a lot more to you in that little phrase, than trying to explain a whole lot about not being grateful for what you have until facing the possibility of never seeing it again. Movies are an integral part to the current cultural experience of a language and many common phrases may come from movies. Knowing these references may show that you understand more than just the spoken words.
