What is the thing is called?

[HighValue]

It is used in soldering.
https://www.mscdirect.com/browse/tnpla/31780737?&cid=ppc-google-New+-+Welding+%26+Soldering+-+PLA&mkwid=s3MdlgWT3%7cdc&pcrid=164124449408&rd=k&product_id=31780737&gclid=EAIaIQobChMIjrKV2ezT9QIVwh-tBh2_UwSaEAQYAiABEgKuh_D_BwE&gclsrc=aw.ds

[Slartybartfast]

It's solder (from the French meaning to join) there are two basic types lead based and silver based. The silver solder is for water pipes the lead is used for things like roofing flashing , stain glass windows and electronics.

I use mostly silver in my electronics but sometimes use lead as it melts at a lower temperature.

[Jessica405]

Solder. For use with a solder gun or soldering iron. Usually it is a mix of lead and tin. It melts at a lower temperature than silver solder, and is used in electronics like printed circuit boards. The solder has a core of flux to clean the surfaces of the items being soldered.

[exitseven]

It is a spool of solder. It is used to connect wires together or to make sweat connections with copper plumbing. It is melted with either a soldering iron or a torch.

[DryGermanGuy]

If you mean „solder“, then this is an actual spool of solder. 🙄

[Justagentuk]

Actually It's that bloke Jaws fromJames Bonds dental floss

[Fireguy17]

solder, could contain lead, or be lead free.
I call it soft solder, it melts at about 400 degrees.

[najekim]

Solder. Used to use 50/50 solder in my metal mixture for molding bullets.

[Agape93]

It's solder wire for a soldering gun

[MCheetah]

It's solder, soldier.

[Citizenkirk]

It's soddar for a motherboard maybe

[Surely]

Can’t help you. I never put copper pipes together!

[TheAfrikan]

That looks like a soldering wire.

[goaded]

Solder.

[slatyb]

Solder.

[AviatorTom]

It's called SOLDER

[Recurrence]

Solder

[Waldoe]

solder