Final answer:
Lithium is a highly reactive metal used for treating manic-depression, distinguishing it from less reactive transition metals utilized in various other applications.
Step-by-step explanation:
The highly reactive metal being referred to for treating manic-depression is likely lithium. Lithium is a highly reactive metal compared to other elements and is used as a medication for bipolar disorder due to its mood stabilizing effects.
Transition metals, on the other hand, exhibit a range of chemical behaviors, some being strong reducing agents and others having lower reactivity, making them useful in various applications such as electronics, catalysts, and jewelry.
Lithium also has the unique ability to penetrate the blood-brain barrier, which is crucial for its use in treating conditions like manic-depression. It can treat manic episodes, helping stabilize mood swings inherent to bipolar disorder.