If you want a clean, high-bitrate file (usually 320kbps or better) that is free of viruses and properly tagged with album art, the official stores are the way to go.
If you stumble upon a website offering a link that requires you to: Monster Imagine Dragons Download Mp3
If you search for on Google, you will find a flood of sketchy websites offering "free" downloads. Warning: Many of these sites are illegal, contain malware, or offer extremely low-quality audio (128kbps or lower). If you want a clean, high-bitrate file (usually