I am in a english class and my teacher says this statement is a metaphor and i just don't agree with him just wondering what you think?
After a sluggish first half, the team finally got on track.
The statement isn't itself a metaphor, but it uses two. The first is such an old metaphor that some people would say it's not one - "sluggish" [="behaving like a slug"]. But many words are based on metaphors if you look back far enough in their history; the word "muscle" means "little mouse".
The second is "on track".
I don't really think it is either - you could stretch and say that the first half was being compared to a slug (sluggish), but it isn't really making that comparison - it's just using that adjective. I'm with you on this one.
I think there is no bright line between idiomatic uses like "on track" or "got off-track" and a metaphor like "the wheels fell off the train."
Since none of the team members literally ran on a track, it's a metaphorical use... or is it an idiom? It's really not clear.
[a writer, not a teacher]