The Sami are the indiginous people of northern Scandinavia ( arriving long before what would become the Germanic ethno linguistic group).
They are Finnic and thus related to Finns, Estonians and so on.
They have many dialects, costumes and groups and where originally nomadic connected to the raindeers grazing grounds.
They dont ALWAYS wear folk costume today any more than Scotsmen wear kilts obviously.
Viking Age Norse where in contact with them, traded and perhaps fought.
There are theories that the Seidr and Galdr magic forms might have been influenced by the Samer.