Simple:
* The children remained quiet during the movie.
* Despite the rain, the flowers remained beautiful.
* The problem remains unsolved.
With prepositions:
* The soldiers remained under fire for hours.
* The book remained on the shelf for years.
* The city remained in lockdown.
With adverbs:
* The painting remained beautifully preserved.
* The king remained stubbornly resistant to change.
* The truth remained sadly hidden.
In different contexts:
* To remain calm: He tried to remain calm despite the stressful situation.
* To remain optimistic: Even though things were tough, she remained optimistic.
* To remain faithful: They remained faithful to their vows.
As a command:
* Remain seated until the announcement.
* Remain silent and listen carefully.
As you can see, "remain" can be used in various ways depending on the context. It expresses a state of staying the same, persisting, or continuing.