The anvil is very important, because it lets you make weapons and armor from bars of ore, like iron or silver ore which is smelted into bars. Metal is classified in tiers.
Copper: Very basic, not much protection.
Iron: Still not much, but strictly better than Copper.
Silver: It does provide SOME protection, but not enough that you dont have to worry about low level enemies.
Gold: Once you have this armor and weapon set, You can ignore slimes and zombies and eyeballs if just walk or jump over them.
Demonite: Only obtained from bosses, this is a VERY good set of armor, which is used with shadow scales (Eater of Worlds) to make shadow scalemail armor.
Meteorite + Obsidian : Obsidian is found when lava and water touch, and Meteorite is found when you break a shadow orb (located in corruption) where a random meteorite falls. Smelt these together in a Hellstone forge (found in lowest part of world) to get
Hellstone: Highest tier armor and weapons, but is almost impsossible to get solo, so get a gang and dig down.
Hope this helped 
