A few nouns in Lithuanian are used only in their plural number. They are called plural nouns. Even though they indicate one object, you need to use the plural endings:

durys (door) - not "duris"
grindys (floor) - not "grindis"
marškiniai (a shirt) - not "marškinys"
metai (a year) - not "metas" (although metas means a time)
miltai (flour) - not "miltas"
žirklės (scissors) not "žirklė"

metai
metų
metams
metus
metais
metuose
metai!

Kokie gražūs metai! What nice year!
Kokiais metais jūs gyvenote Lietuvoje? In what year did you live in Lithuania?
Skambinkite į duris! Ring the door!
Jie perka gerus miltus. They are buying good flour.
Mums nepatinka medinės grindys. We don't like wooden floor.