I recently replaced my 4 x 22" monitors with a 4k TV - giving me back some much-needed desk space. Unfortunately MetaTrader and, more importantly the Auto Trade Manager, looked absolutely awful, with both extra-large and extra-tiny font sizes.
The cure was quite simple and I share this for others thinking of doing same or experiencing similar problems on high-res' screens.
This webpage describes the problem and solution quite nicely but to summarise ...
Backup your registry then press Windows Button + R ; type “regedit” then click OK.
Copy this file to your MetaTrader folder...
Restart your MT.
Just be careful with your regedit - you can create all sorts of grief there. Otherwise it was very simple in the end and my MT4 looks a hell of a lot better on 4k now.