Sir Anthony Caro: On his metal

He is the art student who grew up in the shadow of Henry Moore and came to eclipse him. He is the modernist pioneer of abstract sculpture who can never stop flirting with figurative forms. He has been compared to J M W Turner (though he isn't a painter.) He's a sophisticated theorist about the relationship between sculpture and architecture, who (sometimes) doesn't mind members of the public clambering over his work. He is the inspiration behind all those rusted garden structures you see each year at the Chelsea Flower Show. He is, beyond a doubt, the most significant person who ever came out of New Malden.

Sir Anthony Caro just keeps on going. His career stretches 57 years and shows no sign of ending. He has projects on, this year, in enough different idioms and styles to give a lesser man a breakdown. Now just 84, he is putting the finishing touches to a baptismal chapel in France, and displaying sculptures of his wife's head at the National Portrait Gallery.

Caro and his wife, the painter Sheila Girling, had a successful joint exhibition last year at a Salisbury gallery, where this year he's exhibiting a monumental piece of zigguratted steel called Millbank Steps. The title reminds us that he had a hand in the design of Norman Foster's Millennium Bridge in 2000, although the ziggurat was actually commissioned by Tate Britain for a major retrospective in 2005, just one retrospective among scores he has had since 1967.

In an industry whose high-profile Young British practitioners cautiously disgorge new works every few years, Caro is hectically prolific. He received his lifetime achievement award more than a decade ago. Perhaps its air of finality spurred him into new bursts of creativity.

The exhibition at the NPG is tiny, but significant. It's a series of four bronze heads Caro sculpted in 1988/9, showing his wife in a quartet of moods: Large Head of Sheila, for example, is hunched and fretful, the features twisted while, in Large Head of Sheila – Morning, the mood is quite different, relaxed, smiling, indulgent, the large face resting on a leaning arm. They amount to a moving composite portrait of both a woman and a marriage, a statement of personal feeling in three dimensions.

The baptismal chapel is a project that's been occupying Caro for several years. The church is St Jean de Baptiste in Bourbourg, near Calais. During the war, a damaged British aeroplane, striving to avoid the town's houses, crash-landed on the church roof and set it on fire. The church was later restored, but the choir section remained in ruins until Caro was commissioned to bring it back to life. He's constructed two towers of French oak, 18ft high, to be used for music and singing, a cement baptism font and an array of steel, wood and terracotta niches in the walls. When it opens in October, it will be called the Chapel of Light – the first chapel in France to be given over to one artist's work since Matisse was asked to paint his dancers across the chapel in Vence, behind the Côte d'Azur.

Two exhibitions, one personal and representational, the other sacred and abstract – they represent two sides of an artist who never stopped innovating, never rested on his laurels, and never tired of teasing secret harmonies out of unyielding materials.

He was born in 1924 in New Malden, Surrey, and went to Charterhouse school. His father was a stockbroker who disapproved of arty folk. "Any sort of artist was a dilettante in my parents' book," Caro later recalled. He studied engineering at Christ's College, Cambridge, and in the holidays became apprenticed to the sculptor Charles Wheeler. He joined the Fleet Air Arm during the war, and resumed his studies – this time, at the Royal Academy Schools. He discovered a liking for drawing (but not painting) and for modelling with clay, and in Wheeler's studio found his vocation. Summoning up his courage, he told his father, who replied, "Well, you're going to be very uncomfortable. You're not going to be able to have a family. You're going to live in squalor, but if that's what you want to do..."

While still at the RA, bored by the classical plaster casts and elderly academicians, he found out where Henry Moore lived and called round. The great man took him in and they worked together for two years, casting bronzes in Moore's little cottage in Much Hadham, Hertfordshire, where Caro and his wife Sheila moved in 1951. From 1953, he took up teaching at St Martin's School of Art in London, and stayed attached to the place for 28 years until 1981. His students, along the way, included Richard Deacon, Barry Flanagan, Hamish Fulton, Gilbert & George, Richard Long and William Tucker. His first one-man exhibition was in 1956, in Milan, his first London show following a year later.

Then in 1959, just before his first visit to America, came a fateful encounter with the New York art critic Clement Greenberg. Hearing that Caro had reached a point where his art had to change, Greenberg suggested that, instead of working with clay, he should look at the welded-metal sculpture of the US artist David Smith. In America, on a Ford Foundation grant, Caro met Smith along with Kenneth Noland and other painters, and his life – and the course of English sculpture – was changed.

From 1960 onwards, Caro used to visit dockyards, looking for bits of steel, bolting or welding plates, rods, beams and aluminium tubing into freakish shapes which he then painted in bright yellows, reds and blues, and the occasional sludge-brown. This became the template for his early work: rather than offer a surface that had been worked at, he offered viewers an amalgam of shapes, lines and blocks, yoked into strange new relationships. The new shapes were puzzling, but sensuous, cerebral rather than aesthetic. David Smith had been keen on vertical constructions – he sometimes referred to his pieces as "totems" – while Caro's work was aggressively squat, landscape-mirroring, horizontal, and it made you think.

And, as time went on, Caro did something almost without precedent in sculpture. He refused to bother with plinths or pedestals. His works rested on the floor, sharing a simpler relationship than had existed before between artwork and perceiver. His other great innovation was to paint his sculptures, not just to add random decoration but to give them focus and identity.

In the 1960s, Caro began to teach at Bennington College, Vermont, along with David Smith and the painter Jules Olitski. His first major art show was in 1963 at the Whitechapel Gallery in London, where his 15 large steel abstracts caused a sensation. His star was ascending fast. Writing in 1964, his friend and adviser Greenberg remarked, "Without maintaining necessarily that he is a better artist than Turner, I would venture to say that Caro comes closer to the genuine grand manner – genuine because original and un-synthetic – than any English artist before him." Absurdly high praise, but it was symptomatic of the reverence in which he came to he held in the US.

In the years that followed, Caro restlessly experimented with materials and forms. He still worked in steel, but diversified into bronze, lead, ceramic, silver, wood and paper. In the 1970s he turned to experiments with rusted steel that he varnished or waxed. He spent time in steel factories in Toronto and Brianza, Italy, and employed elaborate steel-handling equipment such as mobile cranes. The result was a series of huge metal pieces that hung in the air or balanced with unearthly lightness above the heads of spectators.

Just when critics had him down as a monumentalist, he began making smaller pieces – table sculptures, lead and wood sculptures, little calligraphic "writing pieces" in steel, wall reliefs in handmade paper – and experimented with "architectural sculpture": his Child's Tower Room was a structure in Japanese oak that the viewer was invited to step inside, to feel its "inner space" – a nice piece of conceptual art for 1984. The next year, after a visit to Greece, he evinced a passion for Greek antiquity and made a series of sculptures based on Hellenic pediments: Scamander, The Rape of the Sabine Women, Xanadu.

He was turning into the king of the major art installation: large bronze or steel structures were commissioned for roof gardens, quaysides, even theatres. Honorary degrees and fellowships, doctorates and a knighthood cascaded down on him like rain. Caro never flagged. In 1999, when he was 75, he displayed at the 48th Venice Biennale a late masterpiece: The Last Judgement, a 25-part sculpture in terracotta, wood and steel, a stark response to the terrors of the century that was about to close. Among a thousand other prizes, he was awarded the Order of Merit, the supreme honour conveyable on a British civilian, an accolade in the personal gift of the Queen. He was the first sculptor to be so honoured since Henry Moore.

It's hard to fathom the scale of his achievement in all this prodigal outpouring of work. In his half-century career, he has reconstituted our ideas of art just as surely as he has reconfigured lumps of steel, wood and tubing into masterpieces of abstract expression. To say he played a pivotal role in 20th-century sculpture, that he inspired and influenced young artists about their choice of materials and the way they might cross boundaries between sculpture and architecture, is only the half of it. He brought about nothing less than a revolution in British art and spent 40 years affirming that it was aesthetically legitimate by creating more and more perfect examples of it.

He has never stopped experimenting, thinking, changing his mind, playing with pure form, embracing the figurative, incorporating myth and history – and always pursuing his simple, unique ambition: "making sculpture more real".

A Life in Brief

Born 8 March 1924, New Malden, Surrey.

Family Married the painter Sheila Girling in 1949. They have two sons, Timothy and Paul.

Education Charterhouse, engineering at Cambridge. Sculpture at Regent Street Polytechnic and Royal Academy Schools.

Career Embraced modernism while working as an assistant to Henry Moore. Tutored at St Martin's 1953-1981 and had his first solo show in Milan in 1956. First major show at Whitechapel Gallery in 1963. Notable retrospectives held in New York (1975), Tokyo (1994), and Tate Britain (2005). In 1998 became the first contemporary sculptor to exhibit at the National Gallery.

He says "I don't think that sculpture belongs in everyday life like a table does, or like a chair."

They say "Anthony Caro is a revolutionary. He changed the face of British sculpture by engaging the spectator. He did this by taking the sculpture off the plinth and placing it in the same space as the spectator." Biographer Ian Barker