Mass. Gen. Laws ch. 43 § 74
The mayor shall be the chief executive officer of the city, commissioner of administration and, ex officio, chairman of the school committee. When present, he shall preside at all meetings of the city council and of the school committee and at all joint conventions thereof.
He may vote on all questions coming before the city council, but shall have no power of veto.
He shall have such other duties, rights and powers as may be provided by ordinance, not in conflict with this chapter.
During the absence or inability of the mayor to act, the commissioner of finance shall, as acting mayor, assume the duties and exercise all the rights and powers of the mayor. In the absence or inability so to act of the commissioner of finance the city council may select another commissioner from their number to perform the duties of acting mayor.
Mass. Gen. Laws ch. 43, § 74