The nibs of drawing tablet pens can be made of different materials. The most common nib material is plastic or felt. The vast majority of pens, by default, have a plastic nib pre-installed.
The reason for different materials is that they greatly impact the sensation of "texture" you experience.
Plastic nibs generally feel smoother when drawing on a given surface. Some of the surface texture will get transmitted through the plastic nib.
Felt nibs provide a little more friction and many people say it can make a tablet surface feel more like traditional paper.
I always suggest giving felt nibs a try, you may enjoy how it feels.
Both kinds of nibs wear over time and the amount of wear depends on how "heavy-handed" you are. But these materials are a little different.
Plastic nibs wear down less.
Felt nibs are more prone to wearing down. Also if you drop your pen and it hits the nib, sometimes I have found that the felt nib can be more easily damaged.
Wacom offers three materials for this pen (standard, elastomer, felt). See this video for an explanation of how standard, elastomer, and felt feel: https://www.youtube.com/watch?v=APAO-yWc_PY
I DO NOT recommend using a metal nib.