要的。可以说做状语的从句、介词短语、不定式短语、分词短语、甚至副词放在句首时都要用逗号与主句隔开。
Before I came to Hangzhuo, I was in Ningbo. 时间状语从句
Though the work is difficult, I don't want to give up. 让步状语从句
In the park, some children are playing with a ball. 介词短语
To be frank, I don't like this place. 不定式短语
Generally , boys like war games. 副词
Entering the room, he saw his uncle lying on the floor. 现在分词
Covered with ice, the road is very slippery. 过去分词
Surprised, Tom opened his eyes wide. 形容词
希望你有所收获。
祝你进步！