The narrator says that, at the funeral, Mr. Hooper's black veil "was now an appropriate emblem."  Black is often associated with death and mourning, and the somberness of the color is fitting for the occasion.  We also often consider there to be a veil over the mysteries of death; they are so close to us but we still cannot see or understand them.  Funerals are solemn and somber occasions where one often considers the mysteries of death and what eternity might be like.  Therefore, the solemnity of the veil is not out of place.

However, when Mr. Hooper presides over a wedding while wearing his veil, "the bride's cold fingers quivered in the tremulous hand of the bridegroom, and her deathlike paleness caused a whisper that the maiden who had been buried a few hours before was come from her grave to be married." The sight of his veil is now completely incongruous to the occasion.  Weddings are joyful events that focus on the life and love that is possible to the living on earth; thus, the veil, a symbol of our inner darkness and sin, is wildly out of place here.  People do not want to think of eternity at a funeral; they want to think of life, the here and now!  Even Mr. Hooper is alarmed by his appearance when he accidentally catches a glimpse of himself in the mirror: "the black veil involved his own spirit in the horror with which it overwhelmed all others," and the minister rushed from the party out into the night.