According to legend, the state's most colourful festival, Onam, celebrates the golden age of King Mahabali, the mythical ruler of Kerala. The festival is to welcome the spirit of King Mahabali, and to assure him that his people are happy and wish him well. The myth goes like this :

The Devas or Gods were worried over the wise and good rule of Mahabali, the Asura king, thinking that he might become too powerful. They sought the help of Vishnu (the Preserver in the Hindu trinity) to curb Mahabali's power. Vishnu, in the form of a dwarf called Vamana, approached him and was offered a boon by the king. The Vamana asked for three paces of land and the king agreed to it. Soon the dwarf began to expand and with the first step, he covered the sky, blotting out the stars, and with the second, he straddled the netherworld. Realising that Vamana's third step will destroy the earth, Mahabali offered his head as the last step. The Gods were glad, but since Mahabali was so attached to his kingdom and the subjects and was very much loved by the people, he was allowed to return once a year.

Onam is considered to be the day when King Mahabali comes from exile to visit his beloved people.

This festivities begin ten days before Thiruonam. A magnificent procession of elephants enthrall you at Trichur (Thrissur). Every festival's end is marked by the bursting of firecrackers. The Kathakali dancers adorned in their colourful garb and bright make-up entertain the crowds at Cheruthuruthy. They depict stories from the epics, Pulikali, also known as Kaduvakali  which is a common sight during the Onam season. Performers painted like tigers in bright yellow, red and black, dance to the beats of instruments like udukku and thakil.

The Vallamkali (boat race) is one of the main attractions of Onam, and is best seen at Aranmulai and Kottayam. About a hundred oarsmen row huge and graceful odee (boats). Oars dip and flash to the rhythm of drums and cymbals in each boat. The songs are generally typical in character and concern people well known in Malabar. Above each boat silk umbrellas are perched : their number denotes the affluence of the family owning the boat. Gold coins and tassles hang from the umbrellas.

In the evening girls perform the Kaikottikkali (Thiruvathirakkali ) in the open, dancing around the traditional brass lamp.

Here follows the malayalam song of Onam which we talks about social justice enjoyed by citizens of Kerala during the time of ruling by the great king Mahabhali, Who considered all the citizens are equal, there  was nothing to hear about lie, cheating or theft and everyone lived happily 

"MAVELI NADU VANIDUM KALAM 
MANUSHARELLARUM ONNUPOLE 
AMODATHODE VASSIKKUM KALAM 
APATHANGARKKUMOTTILLA THANUM 
ADHIKAL VYADHIKAL ONNUMILLA 
BALA MARANANGAL KELKKANILLA 
KALLAVUMILLA CHATHIYUMILLA 
ELLOLAMILLA POLI VACHANAM 
KALLAPPARAYUM CHERU NAZIYUM 
KALLATHARANGAL MATTONUMILLA "