What does Matthew 27:54 mean?

Earlier, Matthew noted that Roman soldiers had been tasked with keeping watch over the men on the crosses. This would have been standard procedure. Crucifixion was a slow, horrific process that could take days. To ensure no one attempted to rescue the person before they died, guards would observe, speed up the process, or otherwise confirm death (John 19:31–34). These same men were likely involved in beating, mocking, and tormenting Jesus that same day (Matthew 27:27–31).

Since then, though, an unnatural darkness had come and gone in the middle of the day (Matthew 27:45). Jesus' death was immediately followed by a dramatic earthquake that seemed too connected to be coincidence (Matthew 27:50–51). That combination of eerie events and the odd taunts of the crowd (Matthew 27:40–43) seems to have terrified the attending soldiers. They might fear they are about to experience divine punishment for their involvement.

It's extremely unlikely pagan soldiers meant they now believed Jesus was the Jewish Messiah, the Christ. More likely, they were echoing His depiction as "Son of God," which they would have heard from the crowd. The Greek of this verse can also be translated as "a son of God," or "a son of a god." Roman mythology allowed for the idea of demigods and other partially divine beings. Pilate also expressed fear when he heard Jesus associated with this idea (John 19:7–8). In any case, their experiences were deeply humbling, and pulled them towards some level of faith in Jesus (John 12:32).