Michael Patrick Gibbs was born in St. John's on 25 March 1870, the son of John and Marguerite (Murray) Gibbs. After receiving his early education from the Christian Brothers at St. Patrick's Hall schools, in 1885 he began the study of law with Michael Carty, the Tory representative after 1889 for the west coast District of St. George's. In 1895 he was admitted as a solicitor to the Supreme Court and the following year called to the Bar. On 30 May 1898 he married Barbara Mary Eadie and they had two sons and two daughters. His son James joined him in 1928 in his law firm.

Gibbs' professional association with Carty evidently led him to become active in the Tory Party. In 1892 he was secretary of the Tory-dominated Tenants League, which had been formed after the 8 July 1892 fire in St. John's to press for land tenure reform through the creation of a land court. However, the Liberal Administration of Premier William Whiteway rejected this suggestion, that would have enabled tenants to negotiate more equitably with their British absentee landlords. In 1893 he was the editor of the Terra Nova Advocate and an unsuccessful candidate in the District of Harbour Main in the general election held in that year. In 1897 he won the election by acclamation in the District of St. George's, a seat in which Carty had decided not to seek re-election. Three years later he lost the District to Carty's brother, George (a Liberal), by eight votes.

It was in the assistance given to the formation of labour unions in the early 1900s that Gibbs was to leave his mark on the political and social life of St. John's. In 1903 he provided legal advice to the city's longshoremen who had struck the Water Street mercantile firms for higher wages. Through his efforts the men formed a union the Longshoremen's Protective Union (LSPU) and won a wage increase. Gibbs became the Union's solicitor and held this position until his death; in doing so, he was able, as one labourer leader later noted in a brief history of the LSPU, to protect the men from "extreme radical doctrines" and to direct their "minds and hopes... to fields of thought imbued with Christian principles." In a 1909 speech to the city's St. Andrew's Club, Gibbs denied public criticisms that he was a socialist, but was, instead, a liberal interested in bettering "the condition of the worker." Besides the LSPU, Gibbs helped to form other unions for city workers.

While he did not receive any financial remuneration in 1903 in helping the LSPU, his ensuing popularity among workers did enable him to win the mayoralty of St. John's in the civic election held on 26 June 1906. He swept incumbent George Shea, who was also the Liberal representative for the District of St. John's East, from office by 2,079 votes to Shea's 1,056. During his mayoralty (1906-1910) he did not seek re-election in 1910 because of his pressing professional and other political commitments Gibbs had the legislature in 1910 enact legislation forcing landlords to improve the sanitation system in the houses they rented to the city's working men. This legislation also provided for greater regulation of working conditions in factories and workshops. In June 1908 Mayor Gibbs found himself in the middle of a brief strike between the Municipal Council and its employees in the sanitary stables, who were represented in negotiations with Council by the LSPU. However, he succeeded in resolving the dispute to both the Council's and the union's satisfaction.

After rejecting overtures in 1907 from Liberal Premier Robert Bond to join the cabinet as Minister of Justice, in 1908 Gibbs joined the People's Party led by Sir Edward Morris, who had resigned from Bond's cabinet the previous year (It was Bond's apparent hope that Gibbs would replace Morris as the champion of the St. John's working class). In both the 1908 and 1909 general elections, Gibbs led the three-man People's Party ticket in the District of St. John's East against incumbent George Shea and two other Liberals. While the People's Party failed to win the District on both occasions, it did win the 1909 election and Premier Morris rewarded his efforts with a seat in 1909 on the Legislative Council, where Gibbs was Government House Leader from 1911-1914. He remained a member of the Council until the suspension in 1934 of Responsible Government. Five years later, he was a member of a committee of prominent St. John's citizens that was formed to press for the restoration of Responsible Government. However, the outbreak of war in Europe quickly muted what criticism there was developing in St. John's to the policies of the British appointed Commission of Government. On 7 November 1943 Gibbs died at St. John's. According to the Observer's Weekly, Gibbs was a "leader ... who fearlessly expresssed his views and whose opinions were widely sought and highly valued."