Why does my iPhone 5s battery drain fast?

Sometimes when I'm not using my phone it would be 96 % if it was at 100 % and I lock the phone and everything.
also only when I'm using it just for music it'll also drain fast. Why does my phone battery drain fast? Is this normal?
It also heats up. I'm wondering if I should take it to the apple store. What do you guys think I should do?

Keep the brightness low. That uses a lot of battery

Dpeends on many things

Some I-phones have a bad battery and you can take it to apple and you can try to qualify for a replacement or refund. Or you can turn the Wi-Fi off when your not connected to it and it saves a lot of battery.

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