The 19-year-old, in his first start for the club at Kingsholm, ran in a hat-trick of tries in Saturday's 45-18 demolition of Bristol.
And Melville said: "He is a special talent. He has got incredible pace and power - he is so very strong.
"His step and his balance means that he can move forward with incredible power, and I am just glad that he is wearing a Gloucester shirt."
Garvey opened his account after 20 minutes, the teenager side-stepping into the narrowest of gaps to sprint for the line.
His second, five minutes before the interval, was his least impressive as he profited from a lucky bounce.
And his hat-trick was finally complete late in the second half when he outfoxed the Shoguns' defence, successfully converting his chip and chase for the score of the afternoon.
The win took Gloucester into a four-point lead at the top of the Premiership ahead of Leeds Tykes.
But Melville refused to get carried away by his team's early season success.
He explained: "Things have gone well today, but we are only four games into the season and there is a long way to go."
Bristol counterpart Peter Thornburn admitted his side were just not good enough to match Gloucester's searing pace in attack.
"We didn't play well enough to win," said Thorburn.
"Gloucester are such a technically sound side with quality players who can turn errors into points in an instant."