How do you hold aggro on multiple mobs?

I wonder how druid tanks do it, i had a lv 70 druid myself once and i always found it hard to tank multiple mobs.
The only thing i did whas swipe lol and hope the mobs stick on me.

But let's say there is a group of 4 mobs in an instance and you are the tank what tactic do you use to hold aggro on all of them?

thank you for reading