After two shaky 1-0 victories in their opening two games against Belarus and Slovakia, the Finnish attack finally started firing on all cylinders against the Swiss.
Jarkko Immonen and Valtteri Filppula each scored twice for the Finns, with Leo Komarov also getting on the scoresheet.
Belarus came from a goal down to beat Kazakhstan 3-2 after a three-goal salvo in the second period also in Helsinki.
Latvia hammered Italy 5-0 in Group S with all the goals coming in just over 40 minutes in Stockholm.
Latvia scored their third goal after Italy conceded three penalties late in the second period and netted two more in the first 2-1/2 minutes of the third period.
Russia struggled to overcome a spirited Germany in a tight encounter in the late game.
When forward Nikolay Zhederov broke the deadlock with just nine seconds to go in the first period many expected the Germans to wilt.
But the expected goal avalanche never came as Germany goalkeeper Dimitri Kotschnew - who also holds a Russian passport - kept them at bay until midway through the third period.
The Germans even outshot Russia by 30-26 during the hotly-contested encounter, with both sides spending 10 minutes in the sin bin for a variety of offences.
Russia doubled their lead when Germany's Justin Krueger was off the ice for slashing, Alexei Tereshenko turning in a pass from Sergei Shirokov to wrap up the win with 10 minutes left.
The United States, Canada and Sweden all enjoyed a rest day.