Historically, almost all coins were made of copper. Nowadays, 1€ coin is mixed with other metals: Inner is 75% copper and 25% nickel, outer is 75% copper, 20% zinc and 5% nickel.
It has an excellent resistance to corrosion and an average lifetime of 30 years. Moreover, its excellent malleability allows to have clear images and distinct edging on coins.
Finally, copper has a very low risk of inducing allergic reactions and it is highly sustainable as it is totally recyclable