There were two storms at Spotless Stadium at Homebush on Saturday. The first was an epic deluge that forced play to be abandoned for nearly half an hour at the end of the first term.

The second was brewed by a Greater Western Sydney side determined not only to show the visitors exactly what it thought of their multimillion-dollar prized signing, but also that - finally, genuinely - it is the force in the competition it promised to be.

The big story going into the match was Lance Franklin's debut for the Swans. Instead, the day will be remembered for having produced an unforgettable result in AFL history.

''You can have your $10 million man,'' may well have been the message booming out of western Sydney. ''Our future is very bright, thank you very much.''

Amid the growing storm above, the Swans took a 38-25 first-quarter advantage, including one goal to Franklin, who drew heated attention all evening, as Giants teammates helped full-back Phil Davis, who had the job on the bearded full-forward.

After an extraordinary 23-minute delay when a powerful storm engulfed the ground, Greater Western Sydney came out firing and won the second term to narrow the margin to seven points - 7.8.50 to 7.1.43 - at half-time.

Yes, the Giants had had less of the ball, but it didn't matter. They were winning the clearance and tackle counts, playing to the strong suit, indicative of what lay ahead.

In the third, the Giants were magnificent, tackling and chasing furiously. They scored 16 points to 12 and left the Swans out-muscled, out-enthused and looking beaten. They received an appropriate ovation from an appreciative audience of 17,102, with the score 9.8.62 to 9.5.59.

The fourth was a match in itself. Four times the Swans came close to scoring but managed just singles as their puff waned.

Instead, the magic came at the other end. Seventeen minutes in, Stephen Coniglio slid a goal through, levelling the scores and producing the first ever chant of ''Giants! Giants!'' at Homebush.

Two minutes later, from another fearful scrap, Adam Kennedy emerged, snapped, and put the Giants ahead for the first time.

Jon Patton's single meant two scores were needed from the Swans. Forget that. A flurry of goals by star forward Jeremy Cameron - his fourth - Sam Frost, Patton and Lachie Whitfield emphatically sealed a win four years in the making.

Certainly, there was no Adam Goodes or Kurt Tippett for the Swans. And, Kieren Jack was ruled out with a sore back. But nothing should take away from a famous win for the Giants.

Even before the bounce, there was a sense of something big.

The sky had turned deep green as thunder clattered and lightning flashed to the west. As if on cue, on the stadium PA, AC/DC's Hell's Bells began.

"I won't take no prisoners, won't spare no lives! I'm gonna get ya, Satan, get ya! Hell's Bells!"

It was the soundtrack to a bitter build-up, which included disputes over the cost-of-living allowance, promotion of the game, sledges between the players and, of course, the small matter of Franklin's allegiance.

The cracking contest began under cracking thunder and lightning. Devon Smith's bomb earned the first points before Sam Reid equalised.

Franklin's first and only kick for the term was the Swans' next goal, after he marked strongly in front of two challengers and nailed a 55-metre shot.

Patton and Toby Greene put the Giants ahead but the Swans exploded with 20 unanswered points.

The Swans led by 13 at the first break before the heavens opened.

The Giants won the second term three goals to one.

After McGlynn potted a free-kick - and the Giants lost Rhys Palmer to a hamstring injury - Cameron sprung to life with a brace, book-ending a dropped mark and a missed shot by Franklin, much to the crowd's joy.

Tom Scully's determined capture of Nick Malceski and subsequent free-kick and goal put GWS within just seven points at the main break.

It won the third, leaving a gap of just three points at the final change, and setting up a gripping final period that will be talked about for years to come.