He was a close friend of Jakob Philipp Hackert and probably accompanied him on study trips to Italy.
It was there that he was commissioned to do a portrait of Queen Sophie Charlotte (who had just married King George III) for display at Gripsholm Castle.
[1] In 1764, as a result of that portrait, he became the court painter for the Grand Duchy of Mecklenburg-Schwerin and was given an apartment in Ludwigslust Palace.
For the remainder of his life, he was on call and kept busy, painting portraits of the ducal family and their relatives.
Matthieu's paintings may now be seen in all of the ducal residences, although some have also been acquired by the Staatliches Museum Schwerin and the Gemäldegalerie, Berlin.