Speed lesson. Go!

に is a particle that sometimes means "to." Like this:

学校に行きます。
がっこう　に　いきます。
(I) go to school.
Literally: "school + に + go."

Sometimes, though, it connects to the masu-stem of verbs to mean "(go) to do something."

We do this by saying:

masu-stem of a verb ＋ に + verb of movement
go to verb

What I mean by "verb of movement" is verbs like "to go," "to come," to return," etc. Those are:

行く（いく // to go）
来る（くる // to come）
戻る（もどる // to return; to go back）

The masu-form of 食べる（たべる // to eat）：

食べます（たべます）

The masu-stem is made by chopping off ます, like this:

食べ（たべ）

So:

食べに行きます
たべ　に　いきます
go to eat // to go for the purpose of eating
Literally: "eat + に (=to) + go."

Example:

今夜は友達と焼肉を食べに行きます。
こんや　は　ともだち　と　やきにく　を　たべ　に　いきます。
Tonight I'm going to go to eat yakiniku with my friend.
Literally: "tonight + は + friend + と + yakiniku + を + go to eat [=eat + に +go]."

But wait!

Though this is most commonly done with the masu-stem of verbs, we can also make sentences like this with nouns that are capable of combining with する (let's call them "する nouns").

食事（しょくじ // meal）
食事する（しょくじする // to eat a meal）

昼休みには、家へ食事にもどります。
ひるやすみ　に　は、　いえ　へ　しょくじ　に　もどります。
I'll go home to eat during my lunch break.
Literally: "lunch break + には, + house + へ + meal + に + return."

Notice that へ in the previous example?

へ is also a particle for "to," like に. The nuance and usage is a little different, though (and a topic for another lesson; when in doubt, use に).

It is worth noting that へ is commonly used when we need a "to" particle before or after the "(go) to (VERB)" phrases that use に.

See the previous or following sentences to see what I mean.

More examples!

こんな時間に何をしに山へ行くの。危ないよ。
こんな　じかん　に　なに　を　し　に　やま　へ　いくの。　あぶない　よ。
What are you going to a mountain for [to do] at this time? It's dangerous!
Literally: "this kind of + time + に + what + を + to do [=do + に] + mountain + へ + go + の. + dangerous + よ."

忘れ物を取りに来ました。
わすれもの　を　とり　に　きました。
I came to get the thing(s) I forgot.
Literally: "forgotten things + を + came to take [=take + に + came]."

Last but not least, let's talk about ために.

When we are going to do something that is NOT an everyday objective, we use ために, as in the following sentence:

来月、ホノルルマラソンに参加するためにハワイへ行きます。
らいげつ、　ホノルルマラソン　に　さんか　する　ために　ハワイ　へ　いきます。
Next month, I'm going to go to Hawaii to participate in the Honolulu Marathon.
Literally: "next month, + Honolulu Marathon + に + participation + do + ために + Hawaii + へ + go."

We'll look at ために more in other lessons, but for now just remember that the に we're looking at in this lesson is used for common actions that aren't too special. Oh also, note that this is different from the ため we saw in this lesson: [NDL #351] - JLPT N4: ため（に）(because of).