Throughout his career, Arnoldi has consistently pushed the boundaries of media and form, experimenting with diverse techniques and materials. His works range from early stick constructions to vibrant, large-scale paintings that explore the interplay of color, shape, and space. Arnoldi's art is included in the collections of the Whitney Museum, Museum of Modern Art in New York, the Los Angeles County Museum of Art, the Smithsonian, and the Guggenheim in Bilbao, amongst others. His ability to merge the physicality of sculpture with the flatness of painting has earned him a reputation as a master of "post-minimal" abstraction, creating pieces that are both visually striking and intellectually engaging.