A metro train

AnonymousIs "the metro" appropriate?

Some Engliishes use it; others say 'subway'.

AnonymousCan I also use "a"?

You could.

Mister MicawberYou could.

Thanks. So either would be natural for you as an English speaker, right?

Sorry, Mr Micawber, I meant "is the/a metro TRAIN" (not just the system)

Anonymous The Metro (underground) system was shut down. I was stuck on the metro train."

This is the way I would say it:
Sorry I am late. The entire Metro system was shut down and I got stuck on one of the trains.

Anonymous Sorry, Mr Micawber, I meant "is the/a metro TRAIN" (not just the system)

OK, but that does not affect your question or my response, I think.

OK, thanks!

AlpheccaStarsSorry I am late. The entire Metro system was shut down and I got stuck on one of the trains.

AlpheccaStars's version is very elegant, but I think it's a bit too wordy for this kind of situation.

Given the context, I don't see much of a difference between "a metro train and "the metro train" (we say "subway" here, as MM said).

"I

Xerxes"I got stuck on a Metro train" essentially means that you got stuck on some Metro train,

And that is all that is necessary in the context. It does not matter which train you happened to be on, you would have been late regardless.
I was late because the Metro system shut down when I was on a train.

People in a particular city will normally use the same terminology.
eg They will all say 'the metro' or all say 'the subway'.

ClivePeople in a particular city will normally use the same terminology.eg They will all say 'the metro' or all say 'the subway'.

Or "the Underground" depending on where in the world it is.