MetadataJobProperty extends AbstractProject, while Pipeline (WorkflowJob) doesn't extend it:

Groovy script inside a Pipeline Job:

stage 'testMetadata'
node{

    def testJob = currentBuild;
    properties([[$class :'MetadataJobProperty', 
                values : [[
                            $class: 'StringMetadataValue', 
                            name : 'owner', 
                            value : 'bob'
                        ]]
                ]]);
}

Returns the following error:

[Pipeline] stage (testMetadata)
Using the 'stage' step without a block argument is deprecated
Entering stage testMetadata
Proceeding
[Pipeline] node
Running on master in (...)
[Pipeline]

[Pipeline] // node
[Pipeline] End of Pipeline
ERROR: cannot apply com.sonyericsson.hudson.plugins.metadata.model.MetadataJobProperty to a WorkflowJob
Finished: FAILURE