Overview
Lord mayor is a title of a mayor of what is usually a major city in a Commonwealth realm, with special recognition bestowed by the sovereign. However, the title or an equivalent is present in other countries, including forms such as "high mayor". Aldermen usually elect the lord mayor from their ranks.
Commonwealth of Nations
Australia
In Australia, lord mayor is a special status granted by the monarch to mayors of major cities, primarily the capitals of Australian states and territories. Australian cities with lord mayors are Adelaide, Brisbane, Darwin, Hobart, Melbourne, Newcastle, Parramatta, Perth, Sydney, and Wollongong.
Canada
In Canada, the only town with a lord mayor in the traditional sense is Niagara-on-the-Lake, as recognition of its role as the first capital of Upper Canada. Unusually, the council of Brantford, Ontario took it upon itself to appoint an honorary Lord Mayor Walter Gretzky in addition to the elected mayor. This is the only example of a council granting the cachet itself, rather than it being granted by a higher authority, such as the Crown or national government.
From Wikipedia (CC BY-SA 4.0).