Suits of armor were once so finely wrought that an attacking lance would glance off their smooth metal harmlessly. But then, as the Middle Ages moved into the Renaissance, European kings demanded that the craftsmen finish the armor with elaborate decoration. All the engraving and embossing upset the surface of the armor. A lance would no longer slip away. But that did not matter.

Decorated armor was for show, so that the kings would look majestic and powerful and indestructible, especially in portraits by great painters.

One of the grandest collections of decorated armor belongs to the Royal Armory of Spain. The National Gallery of Art has now brought some of the finest samples of this Spanish armor and placed them alongside portraits of armor-bearing kings and noblemen by such painters as Diego Velázquez, Peter Paul Rubens and Anthony van Dyck. Both National Gallery and Spanish Armory officials say this has never been done before.

The exhibition, “The Art of Power: Royal Armor and Portraits From Imperial Spain,” which closes Nov. 1, is part of an extraordinary Spanish summer at the National Gallery. A second but far different exhibition, “Luis Meléndez: Master of the Spanish Still Life,” closes in late August and goes on to Los Angeles. There is an ironic link between the shows, for Meléndez tried for many years during the 18th century to become a court painter of kings but failed despite enormous talent.

The rare Meléndez exhibition will be featured at the Los Angeles County Museum of Art from Sept. 23 to Jan. 3. The Spanish show of armor and portraits has no other venue than Washington.

The most spectacular piece in the armor show is a helmet designed by the Milanese armorer Filippo Negroli in 1533 for the Holy Roman Emperor Charles V (who was also Charles I of Spain). It is on display to show how elaborate an armorer could be in the Renaissance. Negroli embossed and gilded curls on the top of the helmet and the strands of a neat beard on the bottom so that Charles would seem to show his light brown hair and beard even when he donned the helmet and covered them up.

Charles V’s favorite suit of armor was made by a well-known German armorer, Desiderius Helmschmid of Augsburg, in 1544. It is known as the Mühlberg armor because the emperor wore it when he defeated German Protestant princes at the battle of Mühlberg three years later. It is distinguished by thick gilded bands and a medallion of the Virgin Mary on the breastplate.

A suit’s shine

The Venetian artist Titian painted a full-length portrait of Charles in the armor, but that painting has been lost. Juan Pantoja de la Cruz, a Spanish court painter, made several copies a half-century later, and one is on display alongside the Mühlberg armor. Pantoja’s 1608 copy, which usually hangs in the Escorial library in Spain, makes the gilded stripes stand out against a black patina that covered most of the armor. The portrait’s suit of armor, in fact, seems to shine like burnished leather.

Another suit of armor made by Helmschmid, this for King Philip II, the son of Charles, was celebrated by three noted artists. This armor is known as the flower-pattern suit because it is decorated with wide gilded strips of intricate bluish flowers. Titian painted Philip II in the armor in a full-length portrait in 1550 and 1551. That painting, which did not come to Washington, is regularly displayed in the Prado museum in Madrid.

Rubens, the Flemish artist, used the Titian portrait with the flower-pattern armor as his model when he painted “Philip II on Horseback” almost a century later, between 1630 and 1640. The new painting, which belongs to the Prado, was evidently commissioned by Philip IV when he realized that the palaces in the Madrid area had equestrian portraits of all the Renaissance kings of Spain except his grandfather. Since Philip II was now perched on a horse, Rubens had to add some pieces to the armor in the Titian painting. But he did not render them correctly. He probably examined Philip II’s armor in the Royal Armory but then painted them from memory elsewhere.

A third Prado painting, “Portrait of Juan Francisco de Pimental in Armor,” usually attributed to Velázquez, features the same armor. (Although specialists in Spain believe this is a genuine Velázquez, there is some disagreement about this elsewhere.) As a high nobleman and military commander, Pimental had his own armor. But Velázquez, as a court painter, had the right to borrow Philip II’s flower-pattern armor from the Royal Armory and pose his model in it. The exhibition displays this armor in front of both the Rubens and Velázquez portraits.

Sometimes armor was so decorated that the etched and embossed patterns covered almost every inch of the metal. That is the case with the armor of Emmanuel Philibert of Savoy, who was the commander of the Spanish navy, the viceroy of Sicily and the grandson of Philip II. The armor was made in 1606 by an anonymous armorer of Milan known as the master of the castle.

Van Dyck, the Flemish portrait painter who became a court painter in Britain, was commissioned while traveling in Italy to come to Sicily and paint the viceroy’s portrait. The 1624 painting, lent to the exhibition by the Dulwich Picture Gallery in London, devotes as much attention to the details of the armor in the portrait as to the stern visage of the viceroy.

By the 18th century, gunpowder had left armor useless in war, and it was rarely used in portraits. But Anton Raphael Mengs, a Spanish court painter born in German-speaking Bohemia, employed it in his 1761 painting “Portrait of Charles III in Armor.” Charles III was not naturally majestic; his features made him seem more like an amiable shopkeeper than a king. Mengs countered this in the painting, now part of the collection of the Royal Palace in Madrid, by adorning Charles with the armor, a general’s sash, a commander’s baton, a sword, and a trio of collars and pendants signifying the Spanish Royal Order of the Golden Fleece, the Naples Order of St. Januarius and the French Order of St. Esprit. Charles III was the last Spanish king painted in armor.

Luis Meléndez longed for the right to paint Charles III. He applied four times for a position as a court painter during Charles’ reign but was rejected each time. Acceptance would have guaranteed him income and prestige.

His ability should have led to a position of standing. His father was the director of painting at the forerunner of the Royal Academy of Arts, and Luis was regarded as the most accomplished pupil. But both father and son had personality clashes with the artistic establishment in those days. The two were regarded as arrogant and irascible. The father was dismissed from the faculty in 1748, and the son thrown out of his classes on the same day.

Without royal sponsorship, Meléndez was unable to launch a career as a portrait painter, and he turned to what was regarded as a lesser form of art -- still-life painting. This path reached a climax in 1771, when he received a commission from the king’s son and daughter-in-law to complete 44 paintings of foodstuffs for a new Cabinet of Natural History at the royal palace. But this still did not bring him fortune. He declared himself a pauper in 1780 and died a month later.

The exhibition comprises a self-portrait, demonstrating his rarely used skill at painting the human figure, and 30 still-life paintings. In striking realism, these show innumerable figs and breads and pears and oranges and grapes and cherries and game and fish and melons and wine and other foods mingling with kitchen utensils in myriad displays.

“He had other ambitions,” says Earl A. Powell III, director of the National Gallery, “but luckily for us they were thwarted. I think he is one of the greatest still-life painters in the history of the medium.”