The elections will determine the composition of the Finnish parliament for the 2023 to 2027 session.
The Finnish parliament is unicameral and comprises 200 legislators, parliamentary elections are held every four years. Finnish citizens are entitled to vote from the age of 18.
During the early voting period, 40.5 percent - or 1,731,441 voters - have already cast their vote. Polling stations are located in supermarkets, libraries, schools and post offices around the country.
The cabinet said on Sunday that by law in Finland, national flags will be raised on election day. The first results of the preliminary voting will be announced immediately after the polls close at 20:00 (17:00 GMT).
The votes are counted online and the preliminary results of 100 percent of the ballots will be summed up within about four hours after the polls close.
The Justice Department will release the official and final results on 5 April.
The main struggle is between the ruling Social Democratic Party led by Sanna Marin, the opposition National Coalition Party led by Petteri Orpo and the Finns Party led by Riikka Purra.