Wesley's theology focused on sanctification and the effect of faith on the character of a Christian. Distinguishing Methodist doctrines include an assurance of salvation, imparted righteousness, the possibility of perfection in love, the works of piety, and the primacy of Scripture. Most Methodists teach that Jesus Christ, the Son of God, died for all of humanity and that salvation is available for all; in theology, this view is known as Arminianism. This teaching rejects the Calvinist position that God has pre-ordained the salvation of a select group of people. However, Whitefield and several others were considered Calvinistic Methodists and held to the Calvinistic position. Methodism emphasises charity and support for the sick, the poor, and the afflicted through the works of mercy. These ideals are put into practice by the establishment of hospitals, orphanages, soup kitchens, and schools to follow Christ's command to spread the gospel and serve all people.
The movement has a wide variety of forms of worship, ranging from high church to low church in liturgical usage. Denominations that descend from the British Methodist tradition are generally less ritualistic, while American Methodism is more so, the United Methodist Church in particular. Methodism is known for its rich musical tradition, and Charles Wesley was instrumental in writing much of the hymnody of the Methodist Church.
Early Methodists were drawn from all levels of society, including the aristocracy, but the Methodist preachers took the message to labourers and criminals who tended to be left outside organised religion at that time. In Britain, the Methodist Church had a major effect in the early decades of the developing working class (1760–1820). In the United States, it became the religion of many slaves who later formed "black churches" in the Methodist tradition.
The Methodist revival began with a group of men, including John Wesley (1703–1791) and his younger brother Charles (1707–1788), as a movement within the Church of England in the 18th century. The Wesley brothers founded the "Holy Club" at the University of Oxford, where John was a fellow and later a lecturer at Lincoln College. The club met weekly and they systematically set about living a holy life. They were accustomed to receiving Communion every week, fasting regularly, abstaining from most forms of amusement and luxury and frequently visited the sick and the poor, as well as prisoners. The fellowship were branded as "Methodist" by their fellow students because of the way they used "rule" and "method" to go about their religious affairs. John, who was leader of the club, took the attempted mockery and turned it into a title of honour.
In 1735, at the invitation of the founder of the Georgia Colony, General James Oglethorpe, both John and Charles Wesley set out for America to be ministers to the colonists and missionaries to the Native Americans. Unsuccessful in their work, the brothers returned to England conscious of their lack of genuine Christian faith. They looked for help to Peter Boehler and other members of the Moravian Church. At a Moravian service in Aldersgate on 24 May 1738, John experienced what has come to be called his evangelical conversion, when he felt his "heart strangely warmed". He records in his journal: "I felt I did trust in Christ, Christ alone, for salvation; and an assurance was given me that He had taken away my sins, even mine, and saved me from the law of sin and death." Charles had reported a similar experience a few days previously. Considered a pivotal moment, Daniel L. Burnett writes: "The significance of Wesley's Aldersgate Experience is monumental … Without it the names of Wesley and Methodism would likely be nothing more than obscure footnotes in the pages of church history."
The Wesley brothers immediately began to preach salvation by faith to individuals and groups, in houses, in religious societies, and in the few churches which had not closed their doors to evangelical preachers. John Wesley came under the influence of the Dutch theologian Jacobus Arminius (1560–1609). Arminius had rejected the Calvinist teaching that God had pre-ordained an elect number of people to eternal bliss while others perished eternally. Conversely, George Whitefield (1714–1770), Howell Harris (1714–1773), and Selina Hastings, Countess of Huntingdon (1707–1791) were notable for being Calvinistic Methodists.
George Whitefield, returning from his own mission in Georgia, joined the Wesley brothers in what was rapidly to become a national crusade. Whitefield, who had been a fellow student of the Wesleys at Oxford, became well known for his unorthodox, itinerant ministry, in which he was dedicated to open-air preaching—reaching crowds of thousands. A key step in the development of John Wesley's ministry was, like Whitefield, to preach in fields, collieries and churchyards to those who did not regularly attend parish church services. Accordingly, many Methodist converts were those disconnected from the Church of England; Wesley remained a cleric of the Established Church and insisted that Methodists attend their local parish church as well as Methodist meetings.