A parable, unlike a riddle, is meant to be understood by its hearers, hopefully without further explanation. This parable is about the Jews and their religious leaders and their rejection of the Son of the King, and the acceptance of the Son by the Gentiles, the non-Jews. God the Father is the King and of course, Jesus is the Son. The other servants/slaves are the prophets. The pronouncement of judgment on them (verse 7) came to pass in the years and events surrounding AD70 and the destruction of Jerusalem.
The unmentioned (but implied) bride is the faithful Church of Christ the Son. The last verse says: “For many are called but few are chosen.” The word chosen could also be translated as “elect.” Some would explain this as having nothing to do with the individual’s choice but solely God’s. But in studying the Greek word used I found that as it is used in the New Testament (and especially here in Matthew) it always carries the conotation of “active obedience.” That is to say, all (or nearly all) of humanity is invited to the feast (to accept the salvation freely offered through the blood of Jesus). But many refuse to attend. Some only go through the motions, perhaps even pretending to be happy. But only those who live their lives for the Son are those who are “chosen.”
If you want to be chosen rather than merely called, check your attitude and your priorities and begin to order them according to the revealed Standard of God–His Word, the Bible . . . and His Son.