denki wo tukete, heya wo akaruku simasu.

In everyday Japanese, 電気 can literally mean electricity, but in sentences like this it often means the light or the lights.

So here, 電気をつけて usually means:

• turn on the light
• turn on the lights

This is a very common Japanese way of saying it. Even though the word is literally related to electricity, the natural meaning in context is usually the light fixture / room light.

Because there are two different actions or action parts here, and each one has its own thing affected by it.

1. 電気をつけて

   • 電気 is the thing being turned on.
   • So it takes を.

2. 部屋を明るくします

   • 部屋 is the thing being made bright.
   • So it also takes を.

So the sentence is basically:

• turn on the light
• make the room bright

In English we might not notice this structure as clearly, but in Japanese each verb or verb-like expression marks what it acts on.

つけて is the て-form of つけます.

The て-form is often used to:

• link actions
• show sequence
• make requests
• connect one action to another

Here it links the first action to the second:

• 電気をつけて = turn on the light, and...
• 部屋を明るくします = make the room bright

So the full sentence means something like:

• Turn on the light and make the room bright.
• or I turn on the light and make the room bright.

depending on context.

This is a very important pattern.

明るい is an i-adjective meaning bright.

To say make something bright, Japanese changes the adjective like this:

• 明るい → 明るく → 明るくする

So:

• 明るい = bright
• 明るくなる = become bright
• 明るくする = make something bright

In polite form:

• 明るくします = make it bright

This pattern works with many i-adjectives:

• 大きい → 大きくする = make bigger
• 小さい → 小さくする = make smaller
• 早い → 早くする = make earlier / faster

Both are possible, but they mean slightly different things.

• 部屋を明るくします = make the room bright

  • someone intentionally causes the room to become bright

• 部屋が明るくなります = the room becomes bright

  • focuses on the change itself, not the person causing it

In your sentence, the speaker is describing an action they do: turning on the light and thereby making the room bright. So 明るくします fits well because it is causative in meaning: the subject actively changes the room.

The subject is omitted, which is very normal in Japanese.

Depending on context, it could mean:

• I turn on the light and make the room bright
• Let’s turn on the light and make the room bright
• You should turn on the light and make the room bright

Japanese often leaves out subjects when they are obvious from the situation. So you usually figure it out from context rather than from the sentence alone.

It is one sentence with two connected actions.

The structure is:

• 電気をつけて = turn on the light
• 部屋を明るくします = make the room bright

The て-form connects them, often with a meaning like:

• and
• then
• by doing that

So this can suggest a sequence:

1. turn on the light
2. the room becomes bright / is made bright

The comma just helps readability. It is not required in all cases, but it is common.

This is a very common pair:

• つける = to turn something on
• つく = to come on / be turned on

So:

• 電気をつけます = turn on the light
• 電気がつきます = the light comes on

The first is transitive: someone does something to an object.
The second is intransitive: the thing changes state.

In your sentence, つけて is used because someone is actively turning on the light.

Because 明るい has to change form before する.

With i-adjectives:

• dictionary form: 明るい
• adverbial form: 明るく

That -く form is used before verbs like する.

So:

• 部屋は明るいです = the room is bright
• 部屋を明るくします = make the room bright

You can think of 明るく here as something like brightly, but in this pattern it is better understood as part of make X bright.

Yes, it is grammatically natural.

That said, in everyday conversation, Japanese speakers might also say simpler things depending on the situation, such as:

• 電気をつけます。 = I’ll turn on the light.
• 部屋を明るくします。 = I’ll make the room bright.
• 電気をつけて、部屋を明るくします。 = I’ll turn on the light and make the room bright.

The full sentence is a bit explicit, because turning on the light already implies making the room bright, but it is still perfectly understandable and grammatical.

します is the polite non-past form of する.

So the sentence is in polite style:

• つけて connects the actions
• 明るくします ends the sentence politely

A plain-style version would be:

• 電気をつけて、部屋を明るくする。

The polite version is more appropriate in many textbook, formal, or neutral conversation settings.