Moreau was one of the most influential and highly regarded Symbolists during his lifetime. And he's never quite fallen out of the public's appreciation. It's difficult to define his works under the aegis of a couple of characteristics, but I will say that my favorite paintings of his are full of those florid details that often characterize Symbolist works, such as in Galatea, which, by the way, is based off of one of my favorite myths of the love of Polyphemus (the Cyclops from the Odyssey) for the water nymph Galatea; you can read Theocritus' excellent poem on it here (can't vouch for the translation). And I would be remiss if I didn't add that Moreau at one point taught Matisse.
Goddess on the Rocks
Thracian Girl Carrying the Head of Orpheus on His Lyre