They sometimes gave aid to servants of God including military assistance. They stood in for God in showing God's wrath toward the Hebrews. They even destroyed entire cities of evildoers, such a Sodom and Gomorra. For centuries people have claimed to be in direct communication with angels. Many of the Saints talked to angels.
Angels communicate with humans in many ways.
They may appear directly to the individual to bring a specific message. In biblical times the angels communicated with the prophets through visions. One of the most important ways that angels communicate is through intuition. Many associate this voice with that of their guarding angel. Angels also superimpose themselves on individuals in order to bring a message.