Cameron Munster's late drop-goal sent reigning premiers Melbourne Storm into the NRL preliminary finals with a hard-fought 29-28 victory over South Sydney Rabbitohs.

The Storm twice came from behind in the second half of an enthralling encounter at AAMI Park, where a double from Cheyse Blair and Munster's 77th-minute one-pointer made Melbourne the first reigning champions to begin their Finals campaign with a win since 2004.

Dane Gagai opened the scoring in the corner and Curtis Scott helped restore parity, before Suliasu Vunivalu benefitted from great evasive work from Billy Slater and a superb burst and kick from Brodie Croft for a pair of tries.

A Cameron Smith penalty with George Burgess in the sin bin for a dangerous tackle put Melbourne six points ahead, but Greg Inglis made the most of a mix-up between Vunivalu and Scott to pluck down Adam Reynolds' high kick and barrel through Slater for his second score of the match.

Blair's first came in-between of tries from Robert Jennings and Cameron Murray and the boot of Josh Addo-Carr created his second, which Smith converted to equalise with five minutes remaining.

Munster split the posts from 30 metres to open the narrowest of margins and errors from Sam Burgess and John Sutton meant the Bunnies' wait for a first win in Melbourne continues, with all 15 of their visits ending in defeat.

Having finished the regular season in the top four, though, Souths' get a second chance in a semi-final against either Brisbane Broncos or St George Illawarra Dragons.