Magic Find works on Barrels, Chests, or other Containers that drop items.

As listed below, the maximum amount a character can obtain is around 1167%.

This means that the more you can get, the better is gets.

'% Better Chance of Getting Magic Item' does not increase the Chances of getting an Exceptional or Elite Item, but if you do get an Exceptional/Elite, the chance of that being Magical/Rare will increase.

Increasing your Magic Find Percentage will always help you. Just remember, you can never have enough % Magic Find. Players that wish to find 'good' Rare Items, and more Set and Unique Items will want to invest heavy in this magical bonus. Magic Find can provide a significant increase in the number of Unique, Rare, and Set Items you find. So having 100% Magic Find does not guarantee a Unique/Rare/Set drops. If you find an item that gives 20% Better Chance of Getting a Magic Item, and a Monster has a 2% chance to drop a Magic Item, you will now have 2.4% chance of getting that Magic Item. Note that this is based upon the monsters' chance to drop an item.

Diablo 2 magic finding