**Core Concept**
The question is testing the knowledge of intraocular foreign bodies, specifically their composition and retention. The most common intraocular foreign body retained is typically made of metal, often a result of industrial accidents or gunshots.

**Why the Correct Answer is Right**
The correct answer is a metal foreign body, usually a copper or iron fragment, because these materials can cause significant tissue damage and are often retained within the eye. The eye's natural defenses, such as the corneal epithelium and the blood-ocular barrier, may not be able to remove metal fragments effectively, leading to their retention. In addition, metal foreign bodies can cause secondary damage due to the generation of free radicals and oxidative stress.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because wood foreign bodies are rare and typically do not cause significant tissue damage. Wood is a non-conductive material that may not cause the same level of electrical injury as metal foreign bodies.
**Option B:** This option is incorrect because glass foreign bodies are brittle and may be easily removed from the eye, especially if they are small. However, they can still cause significant damage and may require surgical removal.
**Option C:** This option is incorrect because plastic foreign bodies are generally non-toxic and may not cause significant tissue damage. However, they can still cause irritation and may require removal to prevent complications.

**Clinical Pearl / High-Yield Fact**
It is essential for ophthalmologists to be aware of the composition of intraocular foreign bodies to determine the best course of treatment. Metal foreign bodies often require surgical removal to prevent further damage, while non-metallic foreign bodies may be managed conservatively.

**Correct Answer:** D. Metal foreign bodies are the most common type of intraocular foreign body retained.