In the Christian tradition the cup contains the blood of Christ (consecrated wine) from which everyone drinks. In the Tarot the Ace of Cups contains water and symbolises love and purity and the heart chakra. Also in the legend of the Holy Grail it is Sir Galahad who is the one who is found worthy due to his purity of heart. In some beliefs “water is life” so when we drink from a cup or chalice we are drinking life.
In Wiccan traditions a chalice or goblet is used to represent the feminine aspect in rituals, toasting the Goddess or God. Again in ceremony the drinking of blessed wine allows this power to pass into our bodies. We are one with the sacred. Often in Wiccan traditions the Chalice is used in combination with the Athame (a ceremonial knife) which represents the male principal.