Tauranga opened the scoring with the first of two goals for Dane Stollery in the match before Monne slotted the penalty on 28 minutes and his second right on halftime after an assist from Riley.
The second spell was mostly one-way traffic with Tauranga keeper Tom Pamment not having to make a save of note in the half.
Monne made it 4-0 when he tucked away his hat trick with an easy tap in, and there was time for Dean Styles to score and Stollery to slot his second before the referee put the visitors out of their misery.
Monne was thrilled to score his first hat trick for Tauranga in his third season at this level.
"The first one I tucked it in after an assist from Steffano and the penalty I slotted straight down the middle. The third goal was Steffano again cutting it back to me for a tap in," he said.
Monne was pleased with the improved form shown by the team in recent weeks.
"It has been really good actually. We have just been going on a run lately and managing to win games. Relegation is well out of the way which is good for us.
"It is a beautiful pitch to play on. That is the style of football [coach] Barry [Gardiner] is trying to implement so it is good to put it out on the pitch.
"We are aiming for fifth so well on the way."
Next Saturday things get a little tougher for Tauranga with an away game to ninth-placed Waitemata City but that is definitely another three points well within their capabilities.
Tauranga City 6 (Nathan Monne 28, 45, 60 Dane Stollery 22, 89 Dean Styles 62) Metro FC 0.