Wanting to spring a surprise in the first of seven possible matches, HV 71 took the lead after 10 minutes through Tommi Tikka.
But desperate to make home advantage count, Modo fought back quickly and equalised through Tobias Winberg just over a minute later.
Just six points separated the two sides, who finished in the bottom two places, over the 52-game regular season, and this series was likely to be nervy.
That was certainly the case in a scoreless second period, however, the match opened up in the final 20 minutes.
Three minutes into the third, Mikkel Aagaard took advantage of a powerplay to put Modo in front, before Lukas Jasek did the same to extend the lead to 3-1 with a little over seven minutes to go.
Jamiro Reber scored for HV 71 as they proved they could also respond well to a setback, but having pulled the goaltender in search of a late equaliser, they gave Sebastian Ohlsson the chance to wrap up a 4-2 win for Modo.
Modo will play hosts again in game two on Sunday, before HV 71 will be at home for games three and four.
Playoffs begin with overtime drama
Thursday saw the SHL Playoffs begin with the first matches in the best-of-three eighth finals.
Having scored an overtime winner to beat Rogle on the final night of the regular season to secure their postseason berth, Malmo did the same again to take a 1-0 series lead, winning 2-1 on the night.
This time, Henrik Haapala was the hero, scoring in the sixth minute of the extra period.
Vaxjo also notched a precious overtime winner on the road at Orebro to put themselves in the driving seat for a series win.
With 09:38 on the clock, Felix Robert snatched a 4-3 victory for the Lakers.
Malmo and Vaxjo have the chance to seal a place in the Quarter-finals today, when game two takes place.