The interest to use nanocarbon such as CNTs to reinforce light metals has increased in recent years. Our previous research showed that by adding 0.1wt% CNTs, the mechanical properties of the Mg composites have all been improved up to 40%. However, the results are still below the theoretically predicted value [1-2] due to the CNT agglomerates still existing on the fracture surface of the composites. In this paper we present for the first time using metal coated CNTs to produce such Mg AZ91 composites. In order to effectively disperse CNTs in the Mg melt, we have coated metals such as Pt on the surface of CNTs. TEM and EDX confirm that atomic Pt has been successfully deposited onto CNTs. Different from coating metal layers on CNTs in literature [3], surface decoration of CNT with metals as in this study may provide further benefits. Discrete metal nanoclusters on the CNT surface can help to prevent agglomeration by the simple means of acting as geometrical ’spacers’. This effect is well known in the context of graphene where decoration of exfoliated graphene sheets with Pt nanoclusters was shown to prevent face-to-face aggregation of the sheets [4]. The dispersion ability and stability of CNTs have been improved after the Pt coating. The mechanical properties are all improved compared to the pure AZ91 and to the uncoated CNTs/AZ91 composites. Individual pulled out CNTs can be observed on the fracture surface of the Pt-coated CNT/AZ91 composites under SEM. We attribute this to a better dispersion and a possible improved wettability of CNTs in Mg melt facilitated due to the Pt coating. Simulation of the interactions between different metals and CNTs has also been carried out and the results agree with the experimental data. The simulation results of different metal coatings are used to guide the experimental work. [1] Q. Li et al.Comp.Sci.Tech.69(2009). [2] Q. Li et al,Euromat 2013. [3] N. Du et al.J. Phys.Chem.C 113(2009). [4] N. Park et al App.Phys.Lett.94 (2009)