Magic rate is a value used to determine the magic level of the item dropped by an enemy with the Drop Rate value as well.
Magic Rate follows the following formula:
magic percentage = Magic Rate * 100 rare percentage = Magic Rate * 10 legendary percentage = Magic Rate normal percentage = ( 1 - Magic Rate * 1.1 ) * 100
Example: You kill a monster: Minotaur ( Magic Rate = 0.45 ). The chances of drop are the following:
magic chance = 45% rare chance = 4.5% legendary chance = 0.45% normal chance = 51%
For the exact magic rate of every mob look at: List of All Monsters