Burns's style is marked by spontaneity, directness, and sincerity, and ranges from the tender intensity of some of his lyrics through the humour of "Tam o' Shanter" and the satire of "Holy Willie's Prayer" and "The Holy Fair".
Burns's poetry drew upon a substantial familiarity with and knowledge of Classical, Biblical, and English literature, as well as the Scottish Makar tradition. Burns was skilled in writing not only in the Scots language but also in the Scottish English dialect of the English language. Some of his works, such as "Love and Liberty" (also known as "The Jolly Beggars"), are written in both Scots and English for various effects.
His themes included republicanism (he lived during the French Revolutionary period) and Radicalism, which he expressed covertly in "Scots Wha Hae", Scottish patriotism, anticlericalism, class inequalities, gender roles, commentary on the Scottish Kirk of his time, Scottish cultural identity, poverty, sexuality, and the beneficial aspects of popular socialising (carousing, Scotch whisky, folk songs, and so forth).
The strong emotional highs and lows associated with many of Burns's poems have led some, such as Burns biographer Robert Crawford, to suggest that he suffered from manic depression—a hypothesis that has been supported by analysis of various samples of his handwriting. Burns himself referred to suffering from episodes of what he called "blue devilism". However, the National Trust for Scotland has downplayed the suggestion on the grounds that evidence is insufficient to support the claim.