Meteor Head

Meteor Heads are flying enemies that spawn once you enter a meteorite's crash site. They usually spawn in packs of 3-5 and will override other enemies in the area, meaning that no other enemies will spawn as long as there are Meteor Heads around.

Meteor Heads follow typical Flying AI, with the exception that they do not collide with solid blocks and can fly straight through them, making them a difficult enemy without a weapon that can also go through blocks like a Vilethorn.

Meteor Heads will stop spawning once there are only 49 or fewer blocks of the Meteorite left, which is usually about 10-20% of its total size. Because of this mechanic, a player can place 50 or more Meteorite blocks wherever they like to spawn Meteor Heads in place of the normal spawns in an area. Meteor Heads that spawn in the Underground Hallow and Underground Corruption will spawn in great number and drop Souls of Light and Souls of Night respectively.

Meteor Heads also have a very small chance of dropping some meteorite ore, so it is partly possible to farm them for their drops, although after two or three landings players should be able to make everything they can out of it, and in the case of Meteor Shots, better replacements are obtainable later on.

Meteor Heads are immune to the Poisoned and the On Fire! debuffs.

Tips
The suggested way of defeating them is to defend yourself by using your pickaxe. While mining you can hit the Meteor Heads as they're flying towards you, as long they're coming from one direction. Suggested items are a Cobalt Shield to keep you from being knocked around and an Obsidian Skull to prevent damage from the Meteorite itself. If you have a Tinkerer's Workshop, you can combine the two into an Obsidian Shield, providing both benefits and using only one accessory slot. A Grappling Hook or Ivy Whip can be used in place of a Cobalt Shield to hold you in place, and Shadow armor or Feral Claws can increase your pickaxe's swing rate. Also if you have the health for it, and have already entered Hardmode, equipping a Star cloak and nothing that provides immunity to fire blocks allows for a fairly uninterrupted stream of stars falling in most directions around you, which usually kill the meteor heads in one hit.

Another suggested method is based on the fact that they do not respawn instantly. With a high tier weapon you should be able to kill all of them rather quickly, provided they have grouped up, giving you some time to act without their interference.

High-tier weapons like the Dark Lance, Night's Edge or greater found in Hardmode are capable of destroying Meteor Heads in a single blow. A convenient way to get rid of them easily early on is Vilethorn, it can shoot through (or into) walls and kill them in one hit as well. As it drops from Shadow Orb, it is very probable that players will have one before going to mine meteorite.

History
Tête de météore Meteor Head Meteor Head Осколок метеора