Yes, that is my opinion and also the opinion of many of the fathers of the Church. As far as I know, among the doctors, only Saint Thomas argued against Saint Michael being a seraph. The Prince of the heavenly hosts is not only in the highest angelic choir, but he is also, along with Gabriel and Raphael, one of the seven who stand before the throne of God. I have come across pious angelographers who place Saint Michael among the next to the lowest of the nine choirs, the archangels, on account of the fact that Saint Jude, in his epistle, specifically titles Michael, the Archangel. These authors also rightly point out that God loves to exalt the humble, and that the holiness of each angel, though perfect for that particular angel, is not based on their hierarchical rank. This means that a guardian angel could be holier than a seraph if God so chooses to adorn him with such a grace. I do not know about that. How could I? These authors also like to point out that Lucifer was created in grace among the highest of angels, a seraph, and he fell, leading a third of the proud angels into hell with him. I do not think Lucifer was a seraph (angels of love), but rather he was of the cherubim (angels of knowledge). If you are interested you can read why I have such a strong opinion on these two points in my article All Angels Were Not Created Equal. Scroll down to the heading Thrones, Cherubim, and Seraphim and read to the end.