Well, there's a bit of confusion over the term Metis. To my understanding, in Riel's day, it applied - at least, as used by English-speakers - only to the French/First-Nation mixed-bloods. The Scottish/First-Nation mixed-bloods were known as Halfbreeds. This was in the context of the Red River community, in which, by Riel's time, a distinct mixed-blood society had developed, with its own culture, politics, customs, economics, etc. The semantic problem that emerged during our lifetimes is that the term 'Half-breed' came to be recognized as pejorative, so to avoid its usage, the term Metis was expanded to include Scottish Halfbreeds - and soon, anyone of mixed European/First-Nation blood anywhere in Canada (and sometimes beyond). However - here's the particular confusion - it is also still used at times to mean, specifically, mixed-blood people with roots in the Red River community. So, if you can, you have to figure out from the context in what sense the term 'Metis' is being used.

The 'First-Nation' in question, in the Red River context, is often Cree, but not necessarily so.

Historically, many Metis men in the West were involved in transportation, as an industry - whether by canoe, York boat, ox-cart, horse & wagon, truck, or whatever. It would make sense that any big expedition in the West would have Metis workers.