A part of being a Finn is to swear. While it is at times considered to be immature or impolite, using swear words can help the user bring out the nature of their opinion. Finns do not typically (at least to my experience) use intonation in their speech which sometimes makes the interpretation slightly inconvenient. Used at the right time cuss can strengthen ones point, but it’s not a part of proper business etiquette, especially in customer-oriented situations.
Arguably perkele is the best known Finnish swear word. It may originate from the name of the god of thunder Perkwunos, or Ukko in Finnish pagan pantheon. It was used originally as a cry for the god of strength (Wikipedia). Usually perkele is used in situations which require strength, both physical and mental. The word even sounds strong, although it may be a learned thing or because it’s often said with strong emphasis. Perkele.
As shown in the video above, perkele and other curse words are often used to emphasize aggression as well.