MTS is a file extension for AVCHD format that is used to run high definition videos.
Clideo's MTS Merger works online which means that you don't need to download it to your device. It's also completely free for files up to 500 MB.
The tool allows you to combine any number of images and videos together, add music, and adjust the result.
How to combine MTS files
Add MTS and other files
Upload the necessary content from your device by clicking on the big blue button "Choose files".
Another option is to add it from an online source by tapping on the small arrow on the right side of the button.
Join MTS files
You can add more recordings or pics with the help of the menu on the top right. Rearrange them if you need.
Choose an aspect ratio presets among four different ones, and select a crop option. If there are images in your compilation, set their duration — note that it will be applied to all the pics you've added. Tick the "Crossfade" box to make the transition smoother.
Then upload a soundtrack, trim it and set the volume. If the audio is shorter than the video, click on the small infinity symbol.
When you're all done, find a perfect format on the bottom left and click on "Merge".
Download merged MTS
Save the final result to your personal device or a cloud storage account. If some changes are needed, click on "Back to edit" to make them without starting over.