[ssiguy]

There a 5 requirements of being defined a Metro and only 5, they are:
1} Must be for local/regional transit { long distance grade-separated HSR doesn't qualify}
2} It must be electric
3} It must be 100% grade separated
4} It must offer "frequent" all day, two way service, 7 days a week
5} It cannot share tracks with freight {it can share rail corridors but not the track}

The technology choice or whether it's elevated, trenched, tunnelled, or at-grade makes no difference in whether a system is a Metro or not.

Ottawa's Confederation line is a full Metro while Edmonton's, although going underground downtown, is not. If Ottawa extends the line to have some grade crossings in the West it will no longer be a Metro. Conversely Montreal's new REM will be a full Metro but Toronto's RER will not be, at least for the next 10 to 15 years, due to not having complete grade separation and still having freight using some of the tracks. If Toronto gets rid of these issues over the next decades then Toronto will have a Metro/subway system of over 300km. Within about 5 years, Montreal will have by far the largest Metro system in the country.