not really sure what you're talking about in the pic.

transition between the marble and wood? you could try a Schluter Jolly.

they do come in thicker sizes

Is that what you mean? Or do you mean an actual metal threshold?

Thank you, I'm pointing at the floor metal with a red arrow.

that thick piece? that's something custom

looks like brass. find a metal fabricator

That looks like tile edging or like Beth suggested Schluter Jolly.

^^Note that the door, the jambs, the header and column wrap-around all all bronze as well as the threshold.

No where near as classy looking but check out Schulter's "Reno-Ramp" for an affordable, easily accessible and safer alternative. (That strip of bronze looks slippery when wet.)

Reno-Ramp

I have to agree this is something custom to work with the door jamb I think if I am understanding the question. Can you post a picture of where YOU are using the metal please .

@Patricia Colwell Consulting it looks way glossier in the rendering than how I really want it. Thank you

But why would you want to break up the flooring? You don't even need a transition in what is essentially an open space!

It’s a little confusing as your rendering looks to be rather traditional but that detail is quite contemporary- and if the stools straddle that floor detail it will break the aesthetic of what (I think) you’re trying to do. And if the materials are not completely 100% flush that will be a toe stub/chair stub issue.