How do you rank up metal working skill?

To answer your question more directly, ESO limits the recipes based on the primary passive ability for each profession. So for blacksmith, that would be your Metalworking skill. You have to put skill points into it, and meet the level requirement to unlock the next tier recipes.

It's designed that way so you can't just automatically be good at every profession by making items, and limits what items you can make until you've put in enough time for it.

The best way to level up is a mix between 2 things. 1. Smelt ore into Ingots and make items (both don't give a lot of exp), and 2. deconstruct items you find. #2 is much faster at leveling up depending on the item. I think the rarer items give more exp, so blue would give more exp than green. Also the higher items give more exp, but the downside is that you have to go out and find the items (meaning your combat skills need to be high enough).

So i would do a mix of both, when you are out looking for dungeons/loot, harvest the items you need (I.E. ore veins for blacksmithing). Then focus on your daily crafting quests to make items to get a resource map. Those maps will give you several nodes of resources, and give more than a normal node will. It's worth doing, then any items you make or find, deconstruct for more exp. I tend to sell things that have the sell for more gold trait, then scrap everything else.

It's still time consuming, but that should give you a good idea on what to do. Also the daily crafting quests are on the billboard near the crafting stations.