Mass. Gen. Laws ch. 43 § 86
The mayor shall be recognized as the official head of the city for all ceremonial purposes and shall be recognized by the courts for the purpose of serving civil process and by the governor for military purposes. In time of public danger or emergency, as determined by the city council, he may, with its consent, take command of the police, maintain order and enforce the laws; and he shall have all the authority and powers conferred upon mayors by sections eighteen and nineteen of chapter thirty-three. He shall be chairman of the city council and chairman of the school committee. He shall have no power to veto but shall have the same powers as any other member of either such body to vote upon all measures coming before it. He shall perform such other duties consistent with his office and with sections seventy-nine to ninety-two A, inclusive, as may be imposed upon him by the city council. During the absence or disability of the mayor, or during the time such office is vacant, his duties shall be performed by the vice-chairman.
Mass. Gen. Laws ch. 43, § 86