hi
Sorry I have not responded to you before now, having read your question and knowing what you are asking. I am suffering migraines at the moment. Shekinah is the presence of Gd or Gd dwelling. Metatron according to the Spanish Quabbalistic tradition is one of the Seraphim.
There is a lesser known tradition (Nearly extinct) from Eastern Europe, the Chochma Machazeh (Wise Visions) And Metatron is one of Gd's names, in that scheme of things. (The Names are similar to the idea behind the Schem Ha Mephoresh to the Sephardi traditions, but are names rather than distinct beings).
The difference is to do with the notions of how Gd communicates. In the chochma machazeh tradition, the concept is one of a direct discourse with Gd and a prophet, this corresponds to what present acedemics call a "J-hist" (cant use the full name) interaction with Gd. The Quabbalah is more of the Elohimist approach where an angel (Malak) intercedes or relays Gd's will to a prophet.
I suspect you may find a difference in how Metatron would be percieved as a concept between different traditions within Judaism. The Sephardim (Spanish Jews) would see things differently from say the Ashkenaz Jews.
The shekinah is more consistent however, meaning simply Gd's presence or Gd Dwelling.
Hope that helps
Shalom
Sophie.