Can angels speak with humans to guide or warn them?

Angels can take on different forms and speak with some of Allah's righteous servants. Several hadiths indicate this, among them the Prophet's (peace be upon him) saying: "If you were to remain in the state you are in when you are with me and in remembrance [of Allah], the angels would shake hands with you on your beds and in your paths." And Gabriel (peace be upon him) descended in the form of a man and spoke with the Prophet (peace be upon him) while the Companions were watching and listening. Imran ibn Husayn used to be greeted by the angels, and they would visit him. When he cauterized himself, they stopped greeting him, but when he abandoned cauterization, they resumed.