Gustave Moreau (1826-1898) was a French Symbolist painter who specialized in mythological scenes. Symbolism was a movement in the late nineteenth century that's a bit difficult to define. Basically, it's a movement about emotion rather than strict representation. There's a dream-like quality to Symbolist painting, which takes the interiority of Romanticism to new heights, by getting inside the brain!
If you look at a painting by Gustave Moreau, you'll quickly realize that, well, there was a lot going on in the man's brain! Let's start with his Jupiter and Semele:
This painting is as chock-a-block as Hieronymus Bosch's triptych, The Garden of Earthly Delights! The story is relatively simple. Semele, a mortal woman, was tricked by Jupiter's jealous wife Juno (Hera) into asking Jupiter to reveal himself in all his godly splendor. He did so - and Semele was quickly incinerated by his lightning bolts! Jupiter manages to save his daughter with Semele, whom he named Bacchus (Dionysus), the God of wine, fertility and the harvest. This painting is therefore a painting of death - and birth.
But how can we begin to make sense of Moreau - and reliably pick him out at a museum? Well, let's talk about his trademarks:
(1) His paintings are almost universally scenes from mythology or the Bible. Gustave Moreau lived alone in a home purchased by his parents in the 9th arrondissement of Paris - today his personal museum that I encourage you to visit even on a short trip to Paris - and he had only his books to keep him company.
(2) Moreau could draw. His draftsmanship is on par with his contemporary Jean-Léon Gérôme. Unlike Gérôme, Moreau wasn't painting near-photographic scenes from his travels to the Near East, but rather snapshots from his own mind:
Look at that King David painting above and the sheer amount of detail that goes into every inch of the painting, from the sunlight's reflection off of thirty kinds of surfaces, from tile to stamped silver, to the shimmer of David's silks, to the architectural touches that another painter would just dash off.
(3) Moreau often used Renaissance compositions. This early Moreau painting is almost identical in composition to German Renaissance master Lucas Cranach the Elder's various Adam and Eve paintings:
You'll note that some of his figures have an elongated Mannerist quality as well.
(4) Moreau's paintings often incorporate Near Eastern elements. Unlike Gérôme, Moreau never traveled to the Near East, but that didn't stop him from painting it!
This eerie painting of Salome dancing for Herod while imagining John the Baptist's severed head looks like it takes place in some combination of the Dome of the Rock, Ashurbanipal's Palace and the Hagia Sophia! There's a mystical element in many of Moreau's Biblical works - and also a dangerous eroticism, in the forms of femme fatales like Salome and Bathsheba.
Now that you have a bit of a handle on Moreau and his mystical, extremely well-drawn, disturbing, erotic, bizarre paintings, it should not surprise you that André Breton, the founder of Surrealism, was a frequent visitor to his museum in Paris. Moreau was very much a forerunner to Breton's movement.