Beltaine also called May Day is the first of May. It's also the source of the May Pole dance, the May Queen, and probably the birth of many medieval babies.
Beltaine is a fertility celebration. It is for planting/sowing. Usually a May Queen is picked from among the elegable maidens, maybe with a lottery of some sort. The Queen then picks a consort from among the elegable men. These two now represent the fertility of the community. In olden times, they would be expected to conceive a child, which would be viewed as a good sign for the general fertility of the community. In modern days, the expectations are a bit less.
The May Pole dance is done with a large pole with ribbons tied to the top. It is placed into the ground and then people take a ribbon end and dance round the pole, half going one way round the pole and the other half going in the opposite direction, interweaving. The ribbons then weave down the pole. There are variations to the dance among different traditions, some make the erecting of the pole part of the ritual, while others have it already erected. Some traditions incorporate the May Queen and King by tying them up at the bottom of the pole with the ribbons. Some only tie the Queen while others tie them together.
Another Beltaine tradition is the Belfire. A large fire used to jump over. Couples will jump over the fire together to grant them fertility. Today's fertility now encompasses not just births and crops, but the growth of incomes, jobs and other aspects of people's lives.
Any and all of these traditions could and have been incorporated in Beltaine celebrations.