"I'm going to watch a movie" 是表示你打算去看电影的常用说法。
来源：这是一个简单的句型，由动词"to go" 和 "to watch"组成。
例句：
I'm going to watch a movie tonight. (今晚我打算去看电影)
Are you going to watch a movie with me this weekend? (这个周末你打算和我一起看电影吗？)
I was thinking of going to watch a movie, do you want to come? (我打算去看电影, 你想来吗？)