It's difficult to say definitively which metal was the "last" to be discovered, as there are different interpretations of "discovery" and the timeline of discovery can be complex.

Here are some factors to consider:

* Naturally occurring vs. synthetic: Some metals are naturally occurring, while others are synthetically produced.

* Isolated vs. theorized: A metal might be theorized to exist before being isolated and characterized.

* Discovery in specific contexts: The discovery of a metal might be in a specific context, like a certain mineral, or through a specific technological process.

With those caveats in mind, some contenders for the "last discovered" metal could include:

* Technetium (Tc): Discovered in 1937, it is a radioactive metal that doesn't exist naturally.

* Promethium (Pm): Discovered in 1945, it is another radioactive metal that does not occur naturally.

* Seaborgium (Sg): Synthesized in 1974, it is a highly radioactive element with a short half-life.

It's important to note that new elements are still being discovered, and the lines between "discovery" and "creation" can be blurry in the realm of synthetic elements.

Therefore, it's not accurate to declare a definitive "last" metal, as the field of discovery and characterization is constantly evolving.