What does Luke 22:4 mean?

Possessed by Satan (Luke 22:3), Judas intentionally seeks out the chief priests for the purpose of betraying Jesus for money. The priests had no idea how to get to Jesus without facing an angry crowd. They are glad for this help, promising to pay Judas thirty pieces of silver. Judas coordinates with the temple guard as to when and where they will find Jesus apart from the people who would defend Him (Matthew 26:15–16; Mark 14:10–11; Luke 22:5–6).

It's unclear what Judas thinks will happen to Jesus. He seems to have no problem betraying Jesus and watching Him be arrested. Yet when he realizes Jesus' fate, he throws back the money and hangs himself (Matthew 27:3–10). Judas chooses to betray Jesus; it's possible that his possession by Satan was a catalyst to push Judas to do what he'd already decided to do without thinking too much about it.

Judas's name is ironic. "Judas" is taken from "Judah" which means "to throw out a hand in an exclamation of praise." Psalm 55:20–21 describes him in a different way:

My companion stretched out his hand against his friends;
he violated his covenant.
His speech was smooth as butter,
yet war was in his heart;
his words were softer than oil,
yet they were drawn swords.

Most priests are Sadducees and descendants of priestly families who supported Herod the Great and escaped his paranoid persecution. The leader of the temple guard is also a Sadducee. His position comes with a reputation for power and cruelty. The temple guard itself is made of Levites; they are not Roman soldiers.