This article is somehow outdated (images included).
Currently there are only swords available as Melee Weapons in Creativerse ... well, plus the Twig you'll get as your first weapon when entering a new world.
You can see the twig when readying your weapon (TAB is the default key) while not carrying an actual sword, but the twig is not a real item any longer that can be unequipped, instead it's merely a spare weapon when all else is lost.
You can rarely find some crafted swords in randomly spawning Treasure Chests underground - Stone Treasure Chests can contain Wood Swords, Obsidian Treasure Chests can contain Stone Swords, Iron Treasure Chests can contain Obsidian Swords and Diamond Treasure Chests can contain Iron Swords.
Creatures called Things that spawn on corrupted blocks can provide you with Diamond Swords from time to time, either when killing them or harvesting from them when they are your Pets. Keepas might provide you with Wood Swords, Silver Keepas and Golden Keepas with Obsidian Swords.
You will probably craft most of your swords yourself, as whenever you hit a creature with a sword, the weapon will lose a bit of durability until it falls apart completely. Currently (as of April 2017), Creativerse has no repair feature.
So you might want to be prepared and take a new sword with you if your current one hasn't much durability left!
The first weapon you can craft is the Wood Sword from a starting recipe that doesn't have to be unlocked. The Wood Sword provides 10 damage points, and the materials you will need to craft can be collected right away at the beginning of the game. No Power Cells nor crafting stations are required.
The Hidden Temple Sword (inflicting damage points) can be crafted from a crafting recipe that currently (April 2017) can be bought in the store as a part of the Hidden Temple Super Bundle, but is not included in smaller recipe bundles. The crafted sword itself as an item might become part of other Hidden Temple Bundles from time to tome, but these usually do not include the crafting recipe. The Hidden Temple Sword inflicts 70 damage points.
The Medieval Sword can be crafted from a crafting recipe that currently (April 2017) can be bought in the store as a part of the Colossal Castle Super Bundle, but is not included in smaller recipe bundles. The crafted sword itself as an item might become part of other Medieval Castle Bundles from time to tome, but these might not include the crafting recipe. The Medieval Sword inflicts 70 damage points.
Sometimes you might be able to receive special swords during holiday-seasons or events, like the Rainbownator 5000 that has only been available for a limited time via redeem code and might become available again randomly in the future on the forums or via Twitter. Since R41 the Rainbownator inflicts 100 damage points just like the Lumite Sword and now also requires Lumite to be crafted.
The Golden Sword can be made from a crafting recipe that was part of the "Gold Pack" which only early backers (who have once paid for the game) have received on November 11th 2015. It cannot be obtained by new players. Naturally neither the crafting recipe nor the sword itself can be found anywhere on the game-worlds of Creativerse. Only players who own the crafting recipe can craft the sword for others and give it to them, but this will not unlock any crafting recipes. The Golden Sword inflicts 100 damage points just like the Lumite Sword (and requires Lumite to be crafted too).
To use a sword (instead of your starting twig) you must right-click on it in the inventory which will place it into the weapon-slot next to your character's portrait. Afterwards you can switch between weapon-mode, tool-mode and harvest-mode with TAB (default key).
Additionally to melee fighting you can throw stuff for range-fighting purposes:
For anyone interested, the pictures are showing Stone Weapon Racks with different swords inside.