Grace is God calling everyone (both good or bad) to participate in His kingdom wedding banquet. It's free because the entrance price has been paid in full by Christ at the Cross. Grace says, "All are welcome." But that is not the same as saying, "All are Saved". Grace calls everyone, but not everyone will respond to be chosen. Salvation is about being chosen rather than just being called. By grace, God call everyone to come. But it is through faith that those who are called respond and become chosen to enter.
What kind of response is required in order to be chosen? It's simple: we need to exchange our dirty street clothes for the wedding garments provided free of charge at the entrance to the banquet hall. We cannot enter on our own terms; we enter on God's terms. That means getting rid of our old clothes (repentance) and then putting on the new wedding garment (faith/obedience). The story of the man who was found in the wedding hall still in his street clothes represents those who presume on God's grace by not responding to His call in the appropriate way. Grace does not dispense with repentance and faith; grace requires repentance and faith.
This parable is a picture of God's kingdom--everything necessary for our salvation and participation in the kingdom banquet has been done at the Cross. There is nothing left for us to do but to take off our filthy clothes of self-righteousness in exchange for the wedding garment of Christ's righteousness. We can't enter the wedding hall still wearing our old clothes of self-righteousness, for they are unfit for the kingdom. We can only enter wearing the robe of righteousness paid for us by Christ. We just have to ask for it--it's free for all who seek and ask by faith.
So many are called but yet pride has prevented many from being chosen because they refuse to throw off their filthy street clothes. They want God to accept them on their own terms. But without repentance (removal of dirty clothes) and faith (putting Christ's righteous garment), we will not be chosen. If we are not chosen, we are not saved and will be cast into the outer darkness where "there will be weeping and gnashing of teeth" (a reference to Hell).
Let's not confuse being called with being chosen. By grace, God call everyone but it is by repentance and faith we become chosen to participate in the Great Wedding Banquet when Christ returns for His Bride.
Father teach us to respond to Your grace with repentance and faith. Amen.