This is the first public miracle of JESUS and it was a miracle of “Transubstantiation” wherein JESUS changes the substance of water into wine. But not just ordinary wine, the “guy” was the head steward, it was his job to “know” the wine and know how to conduct Jewish marriage ceremony and receptions and he declared this wine to be the best and that the wedding party was changing the protocol of accepted behavior within the reception.
In a discussion on Catholic Radio I heard the commentator state that there is a belief that the groom of this wedding was Luke, who upon hearing the head stewards announcement, pursued to know how this came to be and discovered JESUS and become HIS disciple - so just as Andrew was the very first disciple who ran to get his brother Peter and bring him to JESUS, so perhaps this “steward” was used by JESUS to bring Luke to HIM.
However, in HIS very first miracle JESUS “transubstantiates” water into wine and in HIS last miracle during the Last Supper, JESUS “transubstantiates” HIMSELF into unleavened bread. And each time JESUS provides “us” with the “best” and we have through the wedding of Cana the first of two miracles - like bookends of the salvation message - each pointing us to know that JESUS can “change” us if we are open to knowing and loving HIM.
If you ever encounter a Catholic who deny’s the true presence of JESUS in the Host, then ask if they believe in the miracle of the wedding of Cana. How can you accept that JESUS can do the first and not be able to do the later?