Cariad cyntaf ('First Love') is a heartfelt plea by a lovesick young man to his love, his "bright star". He sings of his beloved's beauty and virtue and the love she gives so joyfully. He asks her to promise him her eternal love, so they can be together forever.
It is a traditional Welsh love song, which made an uncharacteristic appearance at the Last Night of the Proms in 2008, sung by Bryn Terfel as part of a medley of songs from England, Scotland and Ireland as well as Wales.
You can watch a video of the song on YouTube.