Playing just his second game as Melbourne's full-time No.1, Fa'alogo scored two tries in the space of three minutes to hand the Storm victory in Wollongong on Saturday.
The 22-year-old then backed it up with a third try late when he stepped through a tiring Dragons defence, locking in his first career hat-trick in the process.
Trailing 20-18 with 17 minutes to go, Fa'alogo put the Storm in the lead when he left Mat Feagai on the turf by stepping the Dragons centre and going over to score.
Moments later he then burst onto a Cameron Munster ball from 30 metres out and went over untouched, giving Melbourne an eight-point lead.
Jahrome Hughes and Moses Leo also crossed in the late-game charge, ensuring Melbourne enter Friday's grand final rematch with Brisbane undefeated.
The 26-point margin did not tell the full story of the game, with the Dragons again gutsy for large parts of it after their golden-point loss to Canterbury in Las Vegas.
But the hosts also only had themselves to blame for the late capitulation.
Damien Cook put a kick out on the full in the lead up to Fa'alogo's first try to gift the Storm attacking ball, while Ryan Couchman was stripped by Joe Chan before the fullback's second.
Melbourne coach Craig Bellamy had this week praised Fa'alogo's improved fitness on taking over the fullback role full-time, after Ryan Papenhuyzen's shock exit at the end of last year.
The No.1 had an immediate impact on Saturday, with his quick hands putting Will Warbrick over for Melbourne's first after long passes from Hughes and Harry Grant in the lead up.
The Storm then got out to 12-0 before three Dragons tries put them ahead 14-12, only for Grant to snatch the lead back for Melbourne when he darted over at dummy-half.
Halfback Dan Atikinson offered glimpses of hope for the Dragons, twice sending Valentine Holmes over with the centre's second try putting St George Illawarra up 20-18 as an upset loomed.
But Fa'alogo had other ideas, making his mark as the Storm ran in five tries in the final 18 minutes.
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