Well, more or less.

If you get more than 4% of the votes, you start gaining seats in the parliament. To form a government, you need to somehow ensure that you have the support of 50%+ or more of the sitting parliament members, so that you can pass your budget and policies when the parliament vote.

If a party alone got 50%+ this ofc is easy, they just form the government alone and pass their budget and laws that they want - but a single party getting enough to form a one-party government is rare. What usually happens is that the political parties negotiate and compromise to create a coalition with the 50%+ support that ensure that their policies pass parliament.

The end result of this is that we often get "wavemaster" parties, for example after the 1998 election we ended up in a situation where the left block had 48.4% of the votes (Social democrats 36.4%, Left party 12.0%), and the right block had 44.5%. The remaining 4.5% of the votes were for our Green party, which then alone could ride the waves and decide which block who got to rule - so they could put some very hefty demands and managed to get far more of their policies passed than their measly 4.5% election result really should have warranted.

Compared for example to the Left party, which had almost 3 times as many votes as the greens in 1998, but since they are the far left (their old name was "The Left party, the Communists"), no right-wing party will ever make deals with them and they are unable to act as wavemasters, so they they are more or less relegated to always support the Social democrats, who throw them a bone now and then but overall always kept them at arms length.

Now, things have gotten more complicated since then - with the Sweden democrats entering the political arena. Basically all the other parties hate them, and at the same time they've gotten enough support to make sure that neither of the blocks can their own majority (the green party has since 1998 more or less decided to join the left block). Up until the last election, they simply supported the sitting right-wing government without making much fuss (save for a few occasions where they torpedoed some proposals by voting for the left-block).

However, with the election last year, they snagged 12% of the votes and got very confident and announced they'd vote against both blocks as long as they didn't want to decrease immigration - they voted down the newly formed left-block government's budget, forcing them to rule on the right-wing's budget. What kinda should happen if the sitting government being unable to pass their own budget, is that a re-election is supposed to be held - but for a lot of various reasons none of the parties, save for SD, wanted this - so instead the remaining 7 parties formed a pact to isolate SD, where they all agreed to let the biggest block pass it's proposed budget despite not being able to secure 50% of the votes.

So now the whole thing is a mess, where the Left party that used to be relegated to a powerless support-party with little influence suddenly is the wave-master party that can put heavy demands on the budget...

Meanwhile SD are climbing like mad in the polls due to all the right-wing voters being pissed as fuck on how the right-wing political parties are abstaining from voting down all the tax raises etc that the left block have put in their budget, despite having the ability to completely block the left block budget if they wanted to. They now appear to have 20%+ support and the title "2nd largest political party in Sweden"...