"Do you watch movies?"
This is what I have understood so far (correct me if i'm wrong):
が ga is used when:
in connection with arimasu/imasu
in connection with like (好き)
は wa is used, when:
something is described by an adjective
The sentence is a negation or a question
を wo is used when:
the verb interacts with the object (eating, buying, writing something)
with kudasai (ください)
As far as i noticed these rules ALWAYS apply in duolingo up to this lesson.
As I understand it, the question of "を" versus "は" depends on what part of the question is the information for which you are seeking, as the asker of the question.
If you are wonder WHO is watching the movie, i.e. "Do YOU watch movies/Are YOU watching the movie?" then the translation would look like: "映画を見ますか？"
In contrast, if you are speaking to a person who you know does other things and watches other shows but you want to find out if they specifically watch MOVIES, then this translation would be as shown above: "映画は見ますか？"
"Do you watch MOVIES?" vs. "ARE YOU watching a movie?" Let me know if my understanding is incorrect or incomplete :)