The museum boasts a remarkable collection of modern art, including masterpieces by Georges Braque, Fernand Léger, Kees Van Dongen, Paul Klee, Amedeo Modigliani, Joan Miró and Pablo Picasso, reflecting the artistic effervescence at the dawn of the 20th century. From the Fauves and the first tentative steps of Cubism to the emergence of Abstraction and the heyday of Surrealism.

The museum's prestigious modern collection was inherited by Jean Masurel on the death of his uncle Roger Dutilleul in 1956, who had passed on his passion to him. Jean Masurel acquired works by Paul Klee such as ‘17 Gewürze (17 Spices)’ (1932) and ‘Abendliche Figur (Figure in the Evening)’ (1935).

The modern art collection also includes many works of naive art, which gained in popularity after the First World War thanks to the influence of Douanier Rousseau, and resonates with art brut by presenting self-taught artists such as Séraphine de Senlis.

This collection is representative of a troubled period, while at the same time echoing the pronounced tastes of its collectors. It finds its chronological entry point in an uncertain period, reflecting the break between the intellectual and artistic worlds and the institutions and authorities.

Pablo Picasso's famous ‘Spanish Still Life (Sol y Sombra)’ of 1912, for example, destroys the codes of perspective and employs new materials such as ripolin and glued paper. From then on, the work of art flirted with the world of objects. Later, it was artists such as Amedeo Modigliani, whose works Dutilleul held, such as ‘Nu assis à la chemise’ (1917), that illustrated the questioning of canons at the turn of the century.

Since it opened in 1983, the museum has given contemporary art its rightful place through the organisation of temporary exhibitions and numerous acquisitions, in line with the wishes of its donors, who wanted to ‘make the characteristic works of art of our time accessible to as many people as possible’.

The contemporary art collection comprises almost 1,000 works, combining the major figures on the international art scene (Daniel Buren, Annette Messager, Christian Boltanski, etc.) with first-rate artists (Etel Adnan, Petrit Halilaj, Miriam Cahn, William Kentridge, etc.).

The contemporary art collection is structured around a number of key themes: the artist's commitment to, or direct involvement with, the world in order to transform it, the relationship with the object, the exploration of artistic margins and the identification of singular figures.

In 1999, a new page in the museum's history was turned with the donation by the Aracine association - set up by Madeleine Lommel, Claire Teller and Michel Nedjar - of its collection of art brut, comprising more than 3,500 works by 170 artists (Aloïse Corbaz, Henry Darger, Auguste Forestier, Madge Gill, Augustin Lesage, Carlo Zinelli, etc.). The term "art brut", used for the first time in 1945 by the artist Jean Dubuffet, refers to singular productions made by "people with no artistic culture". These include self-taught artists, people with mental or psychological disorders, spiritualists and other "unclassifiable" individuals.

The LaM's singularity is thus affirmed by its desire to shift the focus and offer an open and authentic reading of the plural history of twentieth-century art, taking into account the rise of self-taught and marginal forms of creation in the modern era. As a producer of new and stimulating narratives and imaginaries, the museum advocates a more inclusive approach that recognises the diversity of perspectives.

The museum's collection of art brut is now the largest in France, comprising over 6,000 works.