The Wiccan Sabbat of Beltane is held on May 1st, halfway between the spring equinox and the summer solstice.
Beltane is one of the Sabbats that make up the Wheel of the Year, between Ostara and Midsummer.
Wicca uses old traditioins from many Europran rituals. Beltane is the Wiccan May Day festival, focusing on fertility and its rituals, such as maypole dancing. The Maypole is widely believed to be a phallic symbol of fertility.
It is worth noting that most Pagans have a very different view of sex than modern Americans and to a lesser degree, Europeans. Sex is not 'dirty' or 'immoral', but quite the opposite. Sex is seen as sacred and an act of worship and magick. There is a quote from an invocation of the Goddess that "All acts of love and pleasure are my rites".
SOME Wiccans enact a sexual ritual called the Hieros Gamos from the Greek "holy marriage", wherein the High Priest and Priestess of a Coven or a husband and wife (or even two people in a close relationship) metaphorically become vessels of the God and Goddess and make love in sacred space. This act of holy union raises great energy to spread fertility, abundnce and love far and wide.
A less formal, and very old tradition is called 'Greenwooding', where young lovers go into the forest to make love in the midst of the greenery and power of nature.
The word 'Beltane' comes from the Irish, 'Bealtaine' (pr. byel-tchinna), Although, today it is usually pronounced like it's spelled. The origin of the word is so ancient that the exact meaning is lost to the mists of time, but studies of the ancient Celtic languages and customs give us some clues and the most likely meanings are 'Bright Fire' or perhaps even 'Bel's Fire', Bel being one of the most ancient of European Gods.
Even in the modern Irish language, the month of May is Mí Bhealtaine ("month of Beltane").
The Ancient Celts only celebrated four of the major Sabbats or seasonal festivals, Belaine along with Samhain, Imbolc and Lughnasadh.
Mentions of Beltane can be found in some of the oldest Irish writings, connected to significant parts of Celtic mythology. Beltane marks the beginning of summer. This was the time when cattle were moved from winter to summer pastures.
Great Bonfires were lit. People would walk the cattle between two bonfires and younger men (mostly) would leap over the flames or embers of the waning fires. The flames, smoke and ashes of Beltaine bonfires have great protective powers.
As a final rite to mark the beginning of Summer ( a new beggining) fireplaces were extinguished and then re-lit from embers of the great Beltane bonfires.
As at Samhain (pr. Sow-en), the 'veil between the worlds', this world and 'Other World' or supernatural/spiritual realm, is very thin and the Old Gods and spirits can mingle more closely with us.
These ancient traditions continued well into the 19th century in Ireland, Scotland and the Isle of Man (the three remaining holdouts of Celtic Culture). So these rites are well documented and were easily rekindled in the mid 20th century.
In modern Wiccan celbrations, many participants will still perform the old ritual of leaping over the fire, men and women alike.
Beltane gatherings are and always have been, accompanied by a feast, much like every Sabbat, feasting is a way of celebrating abundance when we have it, or helping to create it when we don't!
After feating, a plate and drink is set outside as an offering to the Sidh (pr. Shee) the Irish word for the Ole Ones, spirits or faeries. (it has other, more specific meanings, but that's more than we have room for here).
Another ancient custom is to gather the morning dew on May first, spreading the water on your face to encourage beauty and maintain a youthful appearance.