H2: Commas with Introductory Word or Words: Use commas after introductory a) clauses, b) phrases, or c) words that come before the main clause. See Writing for Success Section 3.1 pp. 101-102 or RULE 2 the following: https://www.iue.edu/hss/writingcenter/documents/Commas.pdf
When Joe was finally ready to go to work, he realized his wallet was gone.
Near a small stream at the bottom of the canyon, we discovered gold.
Nevertheless, Bob was overjoyed when he learned he had won the lottery.
Introductory phrase that modifies the subject:
Expressing her individuality, Vanessa stormed out of the room.