Proclus is a treasure house of information, and he was so already for his ancient readers. But many of his ideas are not original to him, and thus not as eccentric as often said. Both of these points are illustrated by this short passage on the metals assigned to the planets and its use by the later Neoplatonist Olympiodorus. The latter appeals to the authority of Proclus while in fact depending on some unnamed source (or simply general convention), and supplying his own explanations for the correspondences.
The Greek planetary names: Kronos=Saturn, Zeus=Jupiter, Ares=Mars, Helios=Sun, Aphrodite=Venus, Hermes=Mercury, Selene=Moon.
2 Proclus, On the Timaeus vol. 1, p. 43
Gold, silver and each of the metals, just like all other things, grow in the Earth due to the celestial gods and influence from up there. So, it is said that gold belongs to Helios, silver to Selene, lead to Kronos and iron to Ares.
3 Olympiodorus, On the Meteorology p. 266f
And one should also know this, that the divine Proclus, in his commentaries on the Timaeus, refers the metals to the seven planets, saying that:
(1) Lead is dedicated to Kronos, because it is heavy, gloomy and cool.
(2) Electrum to Zeus, because the stars is well-balanced (eukraton) and life-originating (zōiogonon), and so is the alloy (electrum, made from gold and silver); and the alloy is more venerable than gold, and well-balanced.
(3) Iron to Ares, because it is cutting and sharp.
(4) Gold to Helios, insofar as it is the fount of light.
(5) Copper to Aphrodite, because of its flowery brilliance (anthēron) and because it is close to the Sun, just as bronze is close to gold.
(6) Tin to Hermes, because of the shininess and glittering, and also because it is close to the Moon, just as tin is close to silver.
(7) Silver to the Moon, because when silver is plaed next to gold, it appears to be illuminated by the gold and becomes more luminous, just as the Moon is illuminated by the Sun.