First, welcome to FPN. I hope you enjoy your stay.
Next, try the Kaweco. It is compact (good for trouser pockets), reliable (very simple), lightweight, will work without posting for short notes, posts securely, decent nibs, easy to swap nibs, and fairly inexpensive.
The Kaweco can be used as an eyedropper and you might want to try that at some point because of the ink capacity of the small international cartridges(not much) and there is not 'standard' converter as far as I know that will fit the Kaweco.
I am a Pilot fan and have several of their pens that are known as 'pocket' pens. None are as short as the Kaweco when capped and are from a little to a lot more pricey. The Metro is a good pen but the Kaweco is, IHO, a more versatile instrument.
Which ever you decide you won't be making a mistake.
Again, Welcome aboard.