Metallic and semiconducting fractions of single-walled carbon nanotubes (SWCNTs) attract attention from researchers because they have unique catalytic properties. The catalytic properties of sorted fractions are very important. They are needed to control the properties of metallic and semiconducting SWCNTs. For these reasons, it is important to develop and investigate the sorting process of SWCNTs. The sorting process of SWCNTs leads to metallic and semiconducting SWCNTs, as well as single-chirality samples. They possess new unique physical features, as revealed with a microscopic and spectroscopic techniques. Filled SWCNTs are important materials. Methods of obtaining sorted and filled SWCNTs are currently being developed. They allow for obtaining high-quality samples that are clean from impurities with controlled properties. In this work, the metallic fractions of nickelocene-filled SWCNTs were obtained, and the sorting process was investigated with optical absorption spectroscopy (OAS). It was demonstrated that the sorting process of 1.4 nm diametermixed-metallicity SWCNTs leads to obtaining pure metallic SWCNTs. The OAS spectrum of the nickelocene-filled SWCNTs shows the characteristic peaks of the metallic SWCNTs. These peaks correspond to electronic transitions between the first van Hove singularities of metallic SWCNTs. This confirms the purity of the samples and their applicability for catalysis.