Can i search Google Cloud Storage Bucket using metadata values?

It is possible now to do so with APIs.

Set up CUSTOM metadata:

• Visit Viewing and Editing Object Metadata documentation, for more information.
• Use gsutil setmeta -h "[METADATA_KEY]:[METADATA_VALUE]" gs://[BUCKET_NAME]/[OBJECT_NAME] command.
• [METADATA_KEY] should start with x-goog-meta- as stated in the documentation for custom metadata. So [METADATA_KEY] = x-goog-meta-[CUSTOM_VALUE]. NOTE no spaces in the value.
• [METADATA_VALUE] should also be without spaces. Use _ or -.

Search objects based on CUSTOM metadata of objects using APIs.

This example is for Python, but there are a lot of other languages supported in the Listing Objects documentation.

• List the objects in the bucket Sample Code
• For every object found, list all the metadata. Sample Code
• Instead of printing them, take the blob.metadata part only and convert it to string. If it is a default value it will be None otherwise it will be your set up custom metadata key in JSON format.
• Use the value to perform a == operation to check if it is compatible with the value you are looking for and perform any actions accordingly.
• NOTE: The custom values are saved without the x-goog-meta- prefix. It is used only to determine for the API call when setting metadata that this value is custom. Only the second part will be visible in metadata. e.g. you use x-goog-meta-test_metadata it will be visible as test_metadata.

I have did a little bit of coding myself and this is a Python example doing exactly what I described above. You can find the code in GitHub here.

No, GCS doesn't offer a search feature.