Say you're trying to melt a sword down for metal. Does this sword melt? Is it immune to all fire, or just its own? If it melts, what if it's mixed with more metal?

While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits.

 Does this mean that it deals the extra 2d6 only once on an enemy or will it deal the extra damage multiple times like if you use the extra attack feature of the fighter.

Any attack that hits will deal the 2d6

Quote from ClericalKenku >>

Say you're trying to melt a sword down for metal. Does this sword melt? Is it immune to all fire, or just its own? If it melts, what if it's mixed with more metal?

 That probably would't work because it's very durable, if it did melt it would lose it's magic.

Boy

It’s my first magic item. The sorcerer  in my party created  it, a bit by accident. Mine is a dagger, with a +1d4 fire damage to it. As a 5th level monk it is great to do some magical damage. I can also use it in a cavern or dungeon as a light-source, as my Halfling doesn’t have darkvision. 

The Flame Tongue should be forged in a volcano, and the materials could be:

• brass guard and pommel
• copper handle
• masterwork ruby
• bronze blade
• sulfur 
• blood of a fire snake
• feather of a Phoenix 

As the attunement basic rules state:
Attuning to an item requires a creature to spend a short rest focused on only that item while being in physical contact with it (this can't be the same short rest used to learn the item's properties). This focus can take the form of weapon practice (for a weapon), meditation (for a wondrous item), or some other appropriate activity. If the short rest is interrupted, the attunement attempt fails. Otherwise, at the end of the short rest, the creature gains an intuitive understanding of how to activate any magical properties of the item, including any necessary command words.

So, as I read it, spending the Attunement short rest with the weapon includes a time learning how to use the sword. As they probably already know how to swing the sword/attack with it, I would guess that the short rest spend to attune the item includes the study of the item to learn the command word... as a player/dm i would either describe it as trial and error, or as getting so used to the magical sword that the magic itself tells you the correct word. You could also state that the intense work with the weapon makes you able to see a hidden engraved word on the heft which turns out to be the command word, or that the sword after the attunement feels so bound to you that it lets you choose your command word yourself.

vueh

I want to send my players through the Outer Planes. I think this’ll probably be easy to find for a low price in Phlegethos, because I’m evil.

Wow, I guess this is a good starting magic weapon as this was also my first. 

if you have proficiency in an item, you add your proficiency to the attack roll, you don't need proficiency to use it but you don't get your bonus

What's the command word?

i really want one of these

Ima wizard so swords suck... ima 19 level about to finish mah 9th campaign 

Quote from LZiese >>

So in terms of role play... how does the player learn the command word? Trial and error? Magically via Attunement? After a long quest? Paying off a forge cleric or an artificer?  Love suggestions 

 Probably leveling up

You choose it yourself. It's just there for a bit of flavor.

Would the be considered an open flame? Would it stay lit during a blizzard? 

THIS IS SO COOL

This was my first magic item too.