After the Warriors led 14-0 early, they looked set to be the fourth team to fall victim to a comeback in two days before Metcalf saved them on Saturday night.
With the Dragons able to get scores level at 14-14 with 28 minutes left, Metcalf nailed a 25-metre field goal to win it in Wollongong.
The half's deception was key to the play, standing in the line and seemingly catching the Dragons' unaware as he got the kick away under little pressure.
The Dragons had a shot at field goal with five minutes to play to level the scores, but Valentine Holmes sent it wide before another attacking set went begging.
"Luke practices that deception bit, that he looks like he's playing but he knows what he wants to do," coach Andrew Webster said.
"It was the right call at the right time.
"He will look at his game, we didn't attack well in the second half ... I don't think he or the team will be happy with the attack.
"But I liked that he knew one point was important there. I don't think anyone in the stadium thought he was going to take it but Luke.
"They're always the best and smartest field goals from halves."
Saturday night wasn't Metcalf at his best, but he is a big reason why they are second on the ladder this late in a season for the first time since 2002.
The No.7 got the Warriors' first try, dummying his way through Luciano Leilua and Lyhkan King-Togia to score after impressive lead up play from Erin Clark.
The half also had a role in the Warriors' next, when his cross-field kick was inch perfect and Taine Tuaupiki capitalised in the corner.
Crucially he also kicked three-from-four off the tee, compared to Holmes' one-from-three.
And while the Warriors attack lost its way in the second half, Metcalf was still able to provide the key moment in what has been a breakthrough season.
For the Dragons, it is a case of the same old story after three wins from their opening nine games.
They did well to get back into the contest with a hot start to the second half, and looked like they had all the momentum when Corey Allan levelled the scores.
But this is the third game this year the Dragons have been beaten at the death, and second time a field goal has sunk them with limited kick pressure.
"It's the second game this year we have scored more tries than the opposition and haven't won the footy game, and that really hurts," coach Shane Flanagan said.
"There were a couple of decisions that made it hard for us, not just from the referee but from us. We bombed a couple of tries.
"In the end we had the opportunity to kick goals and kick field goals and we didn't do it.
"The effort is there, they are trying hard. Execution I can question, but not effort."
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