It depends on the specific metamorphic rock and what you're scratching it with.

Here's why:

* Hardness: Metamorphic rocks vary in hardness. Some, like marble (metamorphosed limestone) are relatively soft and can be scratched with a fingernail. Others, like quartzite (metamorphosed sandstone) are very hard and can only be scratched by harder materials like steel.

* Scratching Material: What you use to scratch matters. A fingernail is soft, a steel knife is harder, and a diamond is the hardest known natural material.

So, to answer your question directly:

* You might be able to scratch some metamorphic rocks with your fingernail, but not others.

* You could definitely scratch most metamorphic rocks with a steel knife.

* A diamond could scratch any metamorphic rock.

Let me know if you'd like to explore the hardness of specific metamorphic rocks!