Surely
Certainly, Without Exception, Always, Definitely
adverb
This word looks like a verb but it's not (sorry!). It's an adverb. The kanji itself means certain and the vocab version means all sorts of variations on that: surely, certainly, and without exception to name a few.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
Ra, the Egyptian god asks you: "Can you do it? Are you certain you can build the pyramids?"
"Yes I can ra (かなら). Yes I can," you reply.
必ずする
to definitely do
必ず言う
to certainly say
必ずある
something is certainly there, something certainly exists
必ず毎日歩くことが大切です。
It is important to make sure to walk every day.
次のクラスは、必ず来てください。
Please be sure to come to the next class.
死ぬ前に、必ずワニカニをコンプリートします。
I'll surely complete WaniKani before I die.