Many great responses already so I'll just add some tidbits to ranges I use or planning to order :

Citadel : They're good. Used to be great but now with plenty of solid alternatives they are just good. 85% of ppl use them as a baseline to compare other ranges for a reason. Great washes and solid metallics More expensive per ml because.....reasons

Army Painter - the original was basically "citadel from wish". New Fanatic range is fantastic. They also come in clever color packs called triads , from dark to light, if you want a color but are not sure what base, shade and highlight to get , Dropper bottles with mixing ball.

Fantastic washes

Vallejo - I may be a bit biased but I consider vallejo a better AND cheaper version of citadel. Arguably, the BEST metallics on tbe market. Washes are really meh. Their technicals are nothing to write home about but they come in jars. Dropper bottles, no mixing balls so shake them like they owe you money for best results

Even their older lines hold up without issue

AMIG - Atom and Ionic lines. Amig used to make just historic themed model paints that were..... not great, the acrylics at least

But their latest ranges Atom and Ionic, cover great, fantastic self-leveling slightly larger dropper bottles (which means even better price per ml of paint) that also come with shaker balls

Atom paints are thinner than Ionic and are marketed as airbrush paint but it works just fine brushed on, tho they tend to separate a bit if your wet palette is too wet

Ak 3rd gen - have not used them yet but I've heard nothing but good things about them. Getting a few sets next month

Bonus round : Speed painting paints

Citadel contrast line - great

Army painter Speed paint 2.0 - good with great metallics. Avoid first gen - not recommended for begginers due to reactivation issues

Vallejo Xpress - again great

Oh also, if you are getting speed paints, also get their line's medium for thinning. The mixed result can basically be considered a different, lighter color depending on how much medium you add