Social habits of Finch

Zebra finches are extremely social birds; however, only social with other birds. Typically, zebra finches are shy around people and do not like to be petted or held. Some owners of hand-fed zebra finches attest to birds that are more comfortable with human touch. However, as a general rule, individuals seeking pets that enjoy being held should probably avoid the zebra finch. In their native habitat of Australia, wild zebra finches travel in flocks in the wide open grasslands. Zebra finches in captivity retain this extremely social nature. Zebra finches should be kept in pairs to insure their happiness. A pair of zebra finches will often stay in close physical contact at rest or while grooming or preening one another. Often, however, trouble between a pair of Zebra finches will flare over situations, including but not limited to, sitting on the eggs. One strategy for curbing an aggressive male is to provide him a toy to vent his aggression against.
source: Rick Fulmer