He was born on 20 May 1931 in Trenčín. He spent his childhood in Rajec. He was a painter, working in drawing, painting, graphics and ceramics.

His father belonged to the founding generation of Slovak mathematicians, and his parents wished him to study at the Technical University — but Milan chose to study at the Academy of Fine Arts and Design in Bratislava. After being forced to leave Ľudovít Fulla’s studio in 1952, he continued his studies in Ján Želibský’s studio. He studied from 1950 to 1955. In 1957 he was a founding member of the Mikuláš Galanda Group, whose activities came to an end in 1968.

In 1958, his first solo exhibition at the Cyprián Majerník Gallery was closed on the eve of its vernissage; later, in 1965, he was subjected to harsh criticism from regime-aligned painters for an exhibition at the City Gallery. In 1972 he was expelled from the Slovak Union of Fine Artists.

He later participated in exhibitions of Czechoslovak and Slovak visual art in Paris, Prague, Düsseldorf, São Paulo, Venice, Munich, Berlin, Cologne, Essen, Osaka, Moscow, Novara, Seville, Budapest, Esslingen and New York. He held more than 30 solo exhibitions at home and abroad.

In the 1960s and 1970s he moved towards an expressive deformation of the image of the human being as a sum of psychological energies; in the 1970s a tendency towards lyrical meditativeness prevailed.

He died tragically in a car accident on 23 September 1998, near Voznica (central Slovakia).

In Prievidza, two of Paštéka’s figurative sgrafitos can be found on Fraňa Madvu Street.