It is now be the responsibility of the repository to load and persist models from the database rather than using the model to load and save directly. This can be confirmed by the load and save methods being marked as @deprecated in \Magento\Framework\Model\AbstractModel.
//your model repo, etc...
$_searchCriteria = $this->_searchCriteriaBuilder->create();
$filterA = $this->_filterBuilder->setField( $fieldName ) //Filter by model field name
->setValue( $tagValue ) //Filter value
->setConditionType( 'eq' ) //Comparison operator
$filterGroupA = $this->_filterGroupBuilder->setFilters( [ $filterA ] )->create();
//Filters in the same groups work like OR
//Multiple filter groups work like AND
//Which is why the filter and the group are noted with as [$a]
$_searchCriteria->setFilterGroups( [ $filterGroupA ] );
/** @var Model $_results */
$_results = $this->_modelRepository->getList( $_searchCriteria )->getItems();